[WIP] IBC module and required refactoring

[denalimarsh]

Adding the IBC module is straightforward, with only a few additions in app.go. But in order to use the cosmos-sdk version that includes IBC, extensive refactoring is required. The app compiles, but more changes are needed in order to start the chain.

General

• AppModule and AppModuleBasic changed and needed to be updated for each module.
• acc.GetCoins() is now bankKeeper.SpendableCoins(). Module accounts are now in auth Move ModuleAccount to x/auth cosmos/cosmos-sdk#6029. Most modules' expected keepers had to be updated.

Committee

• couldn't register the Permission interface on gov's codec, see 72d70ff#diff-f837503c9342dcedf3537fe21fed2a4cR20.

Validator Vesting

• validator-vesting changes we've upstreamed to the cosmos-sdk are not available in the IBC commit, see cea1f36#diff-dbafec217e8e604ecbe7a53f14014e98R25.

Simulations (commented out in b62e86b)

• acc.SetCoins() is now bankKeeper.AddCoins(). Our sims use a hacky way to load genesis account balances and should be updated i.e. https://github.com/cosmos/cosmos-sdk/blob/master/simapp/test_helpers.go#L72.
• sim decoders need to be updated, see x/ibc: simulation store decoders cosmos/cosmos-sdk#6247.

Cosmos SDK Version

• this branch uses github.com/cosmos/cosmos-sdk v0.34.4-0.20200528144628-f8bad078b7b3, which was the most up-to-date version when I started the refactor.
• gaia@master is now using github.com/cosmos/cosmos-sdk v0.34.4-0.20200511222341-80be50319ca5.