throw RuntimeExceptions when store() methods throw declared exceptions -- we want callers to put() to be alerted if there are errors.
check if system metadata exists rather than just the id mapping (before creating the entry)
handle entryAdded (to hzSystemMetadata) to store sysmeta to local store when it is not already present
use HashMap, HashSet instead of the Tree* classes that require Identifier objects implement Comparable
added HazelCast MapStore and MapLoader implementation for SystemMetadata