staking,ui: implement live ui updates for ticket price, stats

[buck54321]

As pointed out here, the ticket price does not update as the chain progresses, and we might consider disabling ticket purchasing during initial sync.

Other sync-related tasks to consider are updating of ticket statuses for for tickets in the ticketPage.history, and updating of displayed statistics.

[peterzen]

Would the following approach be acceptable?

• During initial sync:

  • display the Staking box in a disabled state (if the wallet being used has staking support, otherwise keep it hidden)

• After initial sync:

  • Enable staking box/VSP picker/ticket purchasing
  • Periodically (every 10 mins) call updateTicketBuyer() to obtain ticket stats and update staking box

[buck54321]

Add the ticket price data to the (*WalletEmitter).TipChange notification. Can probably add ticket stats there too.