Validator re-jailing issues

[jkilpatr]

Duplicate of althea-net#249 for the repo move.

When a validator unjails themselves, they do not have signed_valsets_window blocks to submit signatures because they are held accountable for validator sets created while they were jailed. Furthermore, you cannot submit signatures while you are jailed, so it's not possible for them to catch up and then unjail themselves.

Current solution:

• Allow jailed validators to submit valset signatures.
• The problem with this is that we need to give validators the caveat that they need to catch up on signing before unjailing themselves. This is an unacceptable mental load for most validators.

Possible solution:

• Forgive jailed validators for any valsets they missed while they were jailed
• Proof that this is not exploitable by someone jailing and unjailing themselves repeatedly or something will be provided by Justin in the comments below.
• There could be other issues that Justin will explore further in another documents.