PDB-84 Update to latest version of PostgreSQL JDBC driver

The PostgreSQL upstream finally has uploaded a new revision of their JDBC
driver, but to a new organisation name on maven it seems:

    http://mvnrepository.com/artifact/org.postgresql/postgresql

As linked from their download site:

    http://jdbc.postgresql.org/download.html

Signed-off-by: Ken Barber <ken@bob.sh>