Fully implement PostgreSQL

[cdc-dpbrown]

It would be helpful to our end-users to have another full-function database option other than MS SQL Server. The downside to MS SQL Server is that it is expensive and may negate the benefit of a free Epi Info 7 to some of our limited resource end-users. PostgreSQL is a free and open-source relational database that is already partially implemented in Epi Info 7.

The classes that handle interactions with the databases implement common interfaces: IdbDriverFactory, IDataSource, and DbDriverBase:IDbDriver. MS SQL Server and MS Access fully implement the interfaces whereas the others only implement enough to read the data for analysis.