Initial checkin of PostgreSQL prototype
Update add_mapping_file

Makes code easier to read, updated some comments and docstrings,
makes all column names lowercase, changes varchar type to NOT have a
length limit
Add docstring, update comments
Remove extraneous try/excepts, calls to map

Also some other comments from @wasade
Merge pull request #8 from adamrp/pg_proto

Initial checkin of PostgreSQL prototype