Homestyx hydra

R1:495092613019

Validate settings before writing them to the user cache

Summary:
Fixes T11960. In D16998 I removed some code which validated settings on read to improve performance, but lost this replacement validation in shuffling the patch stack.

This restores similar validation before we write the cache. This has the same effect, it's just faster.

Also, bump the cache key to wipe out anything that got bitten (like my account on `secure` rendering dates wrong).

Test Plan:
- Edited settings, verified the edits held.
Repository: R1 hydra
Commit Date: Dec 7 2016