Update Cassandra version to 2.1.2 for MagnetoDB

We need new features available in Cassandra 2.1.* to move forvard effitiently

Backup and restore for MagnetoDB for MagnetoDB

We do DB agnostic backup/restore, that is we store backed up data in DB independent format (say, JSON) and do not use C* specific tools. We want to have several options for where to store backed up data, but consider Swift as a primary objective. We only guarantee data integrity on per item basic, that is if batch...