Use Postgres advanced types in Python

Postgres has a lot of useful builtin data types, but only some of them are mapped to Python types when accessing the DB using psycopg2.

Extending the support to other types is not straightforward, and involves the following steps:

• Create a Python class to store the data, e.g. class Point
• Write a function to convert a Point to its SQL string representation, e.g. adapt_point
• Write the inverse function to parse the SQL string representation of a Point and return and instance of a Point, e.g. cast_point
• Finally bind all these functions and types, see register_point_type

The complete code is as follows, also available as a gist: