Define upgrade and fork activation mechanism

[adlerjohn]

To avoid future messes, we should define a mechanism to deploy upgrades (i.e. hard forks, and potentially also soft forks).

https://github.com/cosmos/cosmos-sdk/blob/b4820fe491e91cd95340f2f7b606adab454a7636/x/upgrade/spec/README.md

https://github.com/bitcoin/bips/blob/master/bip-0009.mediawiki

[liamsi]

I'm definitely in favor of using the Cosmos-SDK upgrade module, if feasible. Even if that means some tradeoffs.
https://github.com/cosmos/cosmos-sdk/blob/master/x/upgrade/spec/01_concepts.md

Otherwise, it will cost us time spec this out and implement/execute this correctly. Or, there be dragons 🐲

[liamsi]

ref: #171

[liamsi]

This is still relevant independent of the specs we need to make a decision here and have a proper plan.