CacheProxy refactored, cleaned up

* CacheProxy refactored into three classes. 
* CacheProxy related checkstyle issues fixed. 
* Code duplicates removed.
* LoadAll async behavior is fixed.
* ICache doc improved
* ICache API addition, two async methods
Is this the correct behavior? It could very well be, but can you add a few lines of comment why it is fine to just log the timeout exception on finest.