Add fragment caching around expensive queries

* build_time_history
* recent project performance stats
Fragment caching in most tables, and elapsed time calculated client-side
Added action caching
Clearer jQuery usage and other feedback responses
Switch get param from tag to modified
Add explicit settings for config.cache_store
Checks for @current_build before js
Merge pull request #77 from square/rob/lil-caching

Introduce fragment caching