feat: incentive module proto

[toteki]

Description

This PR has been extracted from #1514 to accelerate merging.

Changes since previous review:

• Renamed BondAmount -> Bond since it contains sdk.Coin field
• Added 4 additional queries PendingRewards(addr), Bonded(addr), TotalBonded(denom), and Unbondings(addr)
• Removed the MsgGovCreateAndSponsorProgram that is still under debate - the separate MsgGovCreateProgram and permissionless MsgSponsor are included in this first version.

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[robert-zaremba]

In general looks good. Let's check in chat if we are good to release v1 with only one reward coin.

[robert-zaremba]

pre-approving.

• let's specify what should happen with a proposal not funded by communify fund, and hanging out for long time (nobody will fund it). I suggest that we can remove it after some time (eg 1 or 2 months)?