Governance fixes

[grarco]

Need to complete the following tasks on governance:

• Rename treasury
• skip tx whitelist for accepted governance proposal code execution #370
• Use end_epoch instead of start_epoch to compute the voting power
• Remove max_proposal_fund_transfer parameter
• Add new max_proposal_period parameter
• Update governance specs
• Add a memo field to the vote (Governance custom proposals #1056)
• Support different types of proposals and votes (Governance custom proposals #1056)

For the proposal types we need to support:

• tally type (validators/delegators, majority, super majority, ..) (ledger, finalize_block)
• expected wasm code or not (VP)
• expected memo or not in votes (VP)
• update the client to generate appropriate proposals and votes

[cwgoes]

@Fraccaman @grarco is this up-to-date?

[grarco]

Yes, currently working on the last two tasks