Added __all__ to generators and updated comments
Mapping properly returns type name or type

In other words, the getType and getTypeName methods work as expected.
Cleaned up generators

It no longer needs to import mappings.
Added a Null code mapping
Simplified type loading by using util
Started using the Null code mapping
Cleaned up imports
Added copyright notices
Added Null code mapping test

Ops, forgot to commit this earlier.