Split out source code generation from Nhapi.Base

Source code generation code should not be part of `nhap.base`. When people use the library, they most likely do not use the source code generation part of it.

Hapi, the java library that this library is a port of does not include the source code generation in its distributed library.

Benefits for this are:
*  `nhapi.base` doesn't need to reference `System.Data.Odbc`.