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
Why don't you call this CacheProxyUtil. That is the general naming convention we use for utility classes (a class where all methods are static).