#1 Abstract DB connection module

[Jordan Kasper]

Currently DBEntity will always use the homegrown DBConn object for connection to MySQL. We should abstract out the connection module so that any connection module could be used which follows some specific format.

This may involve multiple tasks:
- Create abstract DBConn class
- Implement DBConn with MySQL specific class (and any others)
- Change DBEntity to accept a DBConn object somehow