Add support for common databases

[robrua]

The Orianna Datastores project is a repository for ready-to-use integration of Orianna with common databases. Currently, this only supports MongoDB at the dto layer.

Support for other popular databases should be built out, both at the dto and data layers. Here's my current list of the highest priority popular databases to support:

• MongoDB (data layer)
• Redis
• Hibernate (or maybe have implementations for specific SQL-like databases)
• Memcached