[RFC-191] Add governorAdmin flag

[goran-ethernal]

Description

Added a new flag to genesis command, called --governor-admin.

It specifies the address of an admin for governance contracts. Given admin can add new addresses to the list of proposers of new governance proposals, and can add new addresses to the list of executors of accepted proposals.

On genesis, and contract deployment, we will set the initial list of proposers and executors of governance proposals to the genesis validator set. Later, when the chain is live, specified governor admin, can add new addresses and remove old ones.

If governor admin address was not specified, zero address will be set as admin, and no new proposer and executor or governance proposals can be added later when chain is live (the genesis validator set will remain forever as possible proposers and executors).

Changes include

• Bugfix (non-breaking change that solves an issue)
• Hotfix (change that solves an urgent issue, and requires immediate attention)
• New feature (non-breaking change that adds functionality)
• Breaking change (change that is not backwards-compatible and/or changes current functionality)

Breaking changes

Please complete this section if any breaking changes have been made, otherwise delete it

Checklist

• I have assigned this PR to myself
• I have added at least 1 reviewer
• I have added the relevant labels
• I have updated the official documentation
• I have added sufficient documentation in code

Testing

• I have tested this code with the official test suite
• I have tested this code manually

[Stefan-Ethernal]

Minor comments to consider.