[WIP] Add more methods to _Deployments contract allowing for multiple versions

[netoneko]

Proposed new methods:

deployVersion() // called after deployService
getVersion() // returns latest version number

allowVersioning()
disallowVersioning()

transferOwnership()
acceptOwnership()

In this model there is no way to completely remove versioning that might be a bit tricky.

Also, there is no migration method in the contract, which also might be problematic.

This PR is a preparation for brainstorming meeting with OdedW

[ronnno]

If we avoid dealing with state upgrades, I'd at least leave some hooks for manual upgrade code in case it's needed:

1. specify that state persists across contract versions
2. define some callback hook in each contract that can perform state upgrades if needed
   ?

[ronnno]

is there a sense in separating governance concerns to a separate contract? this way a chain owner could deploy the policy contract so that each chain can be configured with different upgrade policy (ie, upgrade delays, upgrade by voting, upgrade appeals, permissions etc..)

[netoneko]

Yeah, I think policy contract is a great idea.