Implement tables and unit tests for sqlalchemy storage backend

This is a translation of the sqlite tables to sqlalchemy.

In addition, there are simple tests for tables creation and
some basic execute operations.

Partially Implements blueprint sql-storage-driver

Change-Id: I2860033c0c3bcc9b965209271af74161f3a62818
Implement DataDriver for sqlalchemy storage backend

Partially Implements blueprint sql-storage-driver

Change-Id: I84b67ac50e88645ef69a42860021d72c86a6d018