Relational wrapper library

[vsreekanti]

Build a wrapper library for relational metadata. The wrapper consists of a set of Ground Structures that contain information about relational entities as well as a set of import and export Python(?) scripts that

This should cover things such including (but not limited to):

• Databases
• Tables
• Columns
• Key constraints

Ideally, we'd like the the Hive Metastore integration in #7 to use this wrapper and augment it with Hive-specific information as necessary.