Issue 47

Added getAll(), putAll() and removeAll() implementations with reader and writer support. The code in the cache layer should be versatile enough so that the store layer has a lot of flexibility on how it wants to load the keys.
As per this: https://groups.google.com/forum/#!topic/ehcache-dev/_yywwwbubFE we have agreed to let Ehcache throw CacheLoader/CacheWriter exceptions as is, without re-wrapping them.