This change adds proto serivces and messages to support new api
implementations for serving bsq, btc or all wallet balances.

- RPC GetBsqBalances will return complete BSQ balance info.
- Message BsqBalanceInfo is proto returned by rpc GetBsqBalances.

- RPC GetBtcBalances wil return complete BTC balance info.
- Message BtcBalanceInfo is proto returned by rpc GetBtcBalances.

- RPC GetBalances returns complete BTC and BSQ balance info.
- Message BalancesInfo is proto returned by rpc GetBalances.

RPC GetBalance remains unchnaged, still returns only the available
BTC balance.  It may be deprecated and removed in a future PR.

This change adds proto wrappers for sending bsq, btc, or all balances
to the CLI.  They will be used in future api method implementations:
getbsqbalance, getbtcbalance and getbalances.

This change adds a proto to support a future api implementation for
getting an unused, bsq funding address.

This change adds the proto to support a future api implementation for
transfering bsq.

This change adds proto support for paying maker fees in bsq or btc.
The implementation will come in a future PR.

- Added makerFeeCurrencyCode field to CreateOfferRequest proto.

- Added isCurrencyForMakerFeeBtc field to OfferInfo proto wrapper.

- Add takerFeeCurrencyCode field to TakeOfferRequest proto.

- Added new method to CLI, split some long msg strings into two lines,
  and added a white space after a braceless else statement.

- Added the gRPC server boilerplate.

- Added the core implementation.

- Added a test, and moved method wallet tests into their own package.

- Added three new methods to CLI:

      getbalances   ...	returns complete bsq and btc balance info
      getbsqbalance ...	returns complete bsq balance info
      getbtcbalance ...	returns complete btc balance info

      The old getbalance method is deprecated and will be removed
      if there is agreement to do that.

- Made the needed changes in the CLI's output formatting classes.

- Added new tests to existing BsqWalletTest, added new BtcWalletTest
  and WalletBalancesTest.

- Added disabled tests for funding a bsq wallet (todo in next PR).

All the boilerplate for this method is included in this change, but
the implementation in CoreWalletsService#sendBsq is commented out
until the needed logic to send bsq is refactored out of desktop's
BsqSendView class -- to be included in the next PR.

- Added new method to CLI.

- Added the gRPC server boilerplate.

- Added the core implementation, commented out.

- Enabled tests.

Moved just enough code out of BsqSendView to avoid desktop/api
'sendbsq' duplication, at the cost of adding 1 new method to
BsqSendView.

- Created new BsqTransferModel to hold tx details shared by desktop and api.

- Created new BsqTransferService to send bsq using a BsqTransferModel shared
  by desktop and api.

- Uncommented CoreWalletsService#sendBsq implementation.

- Uncommented sendbsq tests.

- Add optional makerFeeCurrencyCode argument to CLI's 'createoffer'.

- Add optional takerFeeCurrencyCode argument to CLI's 'takeoffer'.

- Add isCurrencyForMakerFeeBtc field to OfferInfo proto wrapper.

- Pass fee currency argument down to CoreOffersService and CoreTradesService's
  create and take offer methods.

- Add maybeSetFeePaymentCurrencyPreference method to OfferUtil to
  conditionally set the 'payFeeInBtc' preference before creating
  or taking an offer.

- Adjust affected tests.

This change fixes the recently bloated wallet balances api.  Now there
is one CLI getbalance [bsq|btc] method that calls a getbalances(currency-code)
on the server.  The server returns full wallet balance information for
BSQ, BTC, or both if the CLI's currency argument is absent.

- grpc.proto:  Reduced number of getbalance(s) proto services from
  four to one.

- GrpcWalletsService:  Reduced number of getbalance(s) gRPC service
  boilerplate methods from four to one.

- CoreApi, CoreWalletsService:  Reduced number of getbalance(s) gRPC
  service implementation methods from four to one.

- CliMain:  Reduced number of getbalance(s) commands from four to one.

- BalancesInfo: Changed BsqBalanceInfo & BtcBalanceInfo field names
  to bsq and btc, respectively, to make calling their accessors
  more readable, less verbose.

- BtcBalanceInfo, BsqBalanceInfo: Defined static final EMPTY instances
  as place holders in a BalancesInfo returned by the gRPC server, when
  one or the other balance types is not requested.  Would be nice
  to serve Optional.empty() instead, but protobuf does not support
  it or null.

- Adjusted affected api tests and build doc.

Returns a list of supported payment method IDs.  This gives CLI users
the correct payment method id for creating a new payment account.

- Added gRPC service GetPaymentMethods to grpc.proto.

- Added gRPC boilerplate method to GrpcPaymentAccountsService.

- Added implimentation to CoreApi -> CorePaymentAccountsService.

- Refactored PaymentAccountTest hierarchy.

- Add api method to CLI.

Had to change the getPaymentMethods() names to getPaymentMethodIds() to
avoid this codacy issue:

"Unnecessary use of fully qualified name 'PaymentMethod.getPaymentMethods'
due to existing static import 'bisq.core.payment.payload.PaymentMethod.*'"

If 'PaymentMethod.getPaymentMethods' was changed to 'getPaymentMethods',
a recursive loop would result, ending in an out of stack heap crash.

This renaming of the method on the server is correct, but the CLI's
'getpaymentmethods' name was not changed.

This reverts commit a465261.

The service side method name change is not correct.

Changed the core getPaymentMethods() -> getFiatPaymentMethods() to avoid

"Unnecessary use of fully qualified name 'PaymentMethod.getPaymentMethods'
due to existing static import 'bisq.core.payment.payload.PaymentMethod.*'"

This class will aid the api's (create) PaymentAccount json form
serialization/de-serialization.

This class does most of the work of the api's (create) PaymentAccount
json form serialization/de-serialization.

This class uses the gson PaymentAccountTypeAdapter to generate editable
json forms for PaymentAccount sub-types, and instantiate PaymentAccount
instances from edited json forms.

In the CLI, this method now takes a single argument, the path to a json
file (a payment account form).  The json text is read from the file
and sent to the server, where it is serialized to a new PaymentAccount
instance, saved, and sent back to the CLI as a protobuf.PaymentAccount.

- Modified existing gRPC boilerplate in grpc.proto and GrpcPaymentAccountsService.

- Modified existing method signatures in CoreApi and CorePaymentAccountsService.

- Replaced existing method impl in CorePaymentAccountsService and
  removed dead code.

- Replaced the CLI's existing 'createpaymentacct' method impl.

- Modified existing tests.

- Add missing boilerplate error handling to GrpcPaymentAccountsService.

- Edit some PaymentAccountForm & PaymentAccountTypeAdapter exception
  messages that would be passed to CLI;  they should be in the same
  style as existing CLI err msgs.

For exceptions caught in the server, we want to log a reason and a
full stack trace, then send less verbose exception msgs up to the CLI.

Restore BsqSendView to version @ commit 48a515b.
Author: jmacxx
Date:   Tue Nov 10 19:35:31 2020 -0600

    Add encrypted wallet password prompt when sending funds from BSQ wallet

    Correct wording of transaction confirmation popup to use 'mining fee'
    instead of 'transaction fee' to make it consistent with wording of
    the BTC confirmation popup.