Two enhancements for SOCI 3.2.3 hotfix, PostgreSQL UUID column support and SQLITE3 error code in exception

Greetings, I submit the following two enhancements for inclusion in the 3.2.3 hotfix or later. 

The first one adds support for PostgreSQL UUID columns in the backend.  Includes unit test to show correctness.

The second is a simple sqlite3_soci_error exception that exposes the SQLITE result code as part of the exception data.

Regards,
Alex Volanis