Enhance cache management methods on EmbeddedCacheManager

These should include:

boolean cacheExists(String cache)
// Old: Cache<?, ?> getCacheIfExists(String cache)
Cache<?, ?> getCache(String cache, boolean createIfAbsent)
boolean remove(String Cache)

Original request:

There seems to be no ability to check if a populated cache exists through both CacheManager and through Cache (=is this still a valid handle) and to get a cache if it exists.