Added implementation for memory db.
Added implementation for memory db.

mschmele/Common-Metadata-Repository,mschmele/Common-Metadata-Repository,mschmele/Common-Metadata-Repository,nasa/Common-Metadata-Repository,nasa/Common-Metadata-Repository,nasa/Common-Metadata-Repository,nasa/Common-Metadata-Repository,nasa/Common-Metadata-Repository,nasa/Common-Metadata-Repository,mschmele/Common-Metadata-Repository