cache restores by default

https://docs.google.com/a/dimagi.com/document/edit?id=1-q8fjg-Vn6gbUoBylcNi_z6z5D21Kn-2V-N7r-4nYF4# for context.

This change:

- Removes the caching setting entirely.
- Always caches the initial responses for 1 hour if they take longer than 1 minute
- Caches all steady-state responses
- Fixes an invalidation bug in the initial caching code that was likely causing many force-syncs (https://github.com/dimagi/commcare-hq/commit/a420d5a6d0a124a8e1e8708ef94e2090fa4d8088)
- Fixes an invalidation bug with commtrack ledgers if there were no case updates (https://github.com/dimagi/commcare-hq/commit/18cffee2cd962b4725964f571469137c76f29fb5)