Contractor refactor

[ChrisSchinnerl]

This issue serves as a collection of ideas / brainstorming issue for a potential contractor refactor. None of these are actionable items but rather unfinished thoughts worth exploring.

Scoring

• Revisit scoring algorithm. Some scores may not make sense anymore and might be better as gouging checks or user defined limits.
• Take into account failed storage obligation when it comes to scoring hosts? One of the few proofs of host reliability that are on-chain.
• Reconsider dropping hosts for having a low score as long as the host doesn't violate gouging settings to avoid churn. Needs something else to compensate for failed interactions or poor performance.

Contract Set

• It might not make sense to keep enforcing a strict limit of 50 or so hosts. Instead this could become a minimum allowing us to punish smaller hosts less and instead just filling up more hosts as necessary. Tricky part is determining when to form new contracts.