Add only queries to the cache key and cache (although the cache will only be looked at for the count).
Move cache key generation to a new function since it's getting pretty long.
Load all records in an only even if we already have some of them (so that filtering works).
Merge pull request #28 from mavenlink/only_in_cache_fetching

Only queries fetch all records
Brainstem.Model has an invalidateCache method to invalidate the caches that the model is a result in.
When a model gets removed from the StorageManager (usually via model.destroy) the StorageManager will invalidate the caches that the model appears in.
Fix invaldiateCache checks.
Merge pull request #29 from mavenlink/cache_clearing

Cache clearing