GS-11741

Initial load entries augmentation, for Hibernate and Cassandra flavors of SpaceDataSource:
* Added logic that prepares a map of  initial load entries names and descriptors (method initialMetadataLoad).
* Added logic that creates partition-specific queries for initial load entries and adds it to the initial load queries collection (method obtainInitialLoadQueries).
* Enhanced code for handling loading of entries and custom-queries (method initialDataLoad). 
* Added feature switch (default: true)
* Unit tests.

Reviewed by Niv

git-svn-id: svn://pc-lab14/SVN/xap/trunk/openspaces@182315 eb64e737-3616-4df0-8941-5ee2ae88103d