New Signature interface available in the top level types package.
auth.StdSignature implements such interface. User defined auth
module can now define their own custom signature types.
Work carried out in the context of the following issues:
- #4488
- #4487
Implement the "CommunityPoolSpendProposal" as described in Cosmos Hub proposal 7.
Also a useful test of Git flow for merging features passed in governance proposals.