Implement 'getAllBinaryKeys()' in InfinispanBinaryStore

For working backup all keys needs to be known. Also these one only exists in CacheStore.

InfinispanUtil.getAllBinaryKeys() needs to be extended to support backup and restore.

The cache store should only be bothered in the following situations (assume CacheLoader is configured):
LOCAL cache: when preload = off or eviction enabled.
REPL cache: when preload = off or eviction enabled. On every node, when store is not shared otherwise only on the current node.
DIST cache: On every node, when store is not shared otherwise only on the current node.

The results of the returning futures have to be merged, otherwise you'll end up with multiple appearence of one key during the iteration.