WIP: Vault End-Point Get/Head Update

DONE:
- Vault Head returns whether or not a Vault Exists
- Vault Get returns statistics on the vault
 - statistics are gathered from the drivers
 - drivers are all stubbed out (at present)
 - sqlite driver provides implementation

TODO:
- Implement MongoDB, Cassandra, Swift, and Disk Storage driver statistics
- Update/Add Tests to complete code coverage
what if we just return the generator and have exception checking outside?