Whitelist changes

[sug0]

Supersedes #59 and #55
Related to anoma/namada#1290

Changes

• Make some nonce fields public (Make nonces public #59)
• Emit old transfer to Namada nonce instead of the updated nonce (Emit the old transfer to Namada nonce #55)
• Remove the token whitelist from the smart contracts
• Add validator set pipelining mechanism to Governance.sol
• Fix the setup scripts
• Fix the tests