Add PostgreSQL support

* Update POM:
  * Add SpringSource packaged PostgreSQL JDBC4 driver (just in case).
  * State UTF-8 source encoding.
* Update Tomcat provided configuration to add sample PostgreSQL DB connection pool configuration.
* Add DDL, DML and instructions for PostgreSQL.
* Update jdbc.properties:
  * Enhance MySQL jdbc.url property to detect and use port if provided.
  * Add appropriate (and commented) properties for PostgreSQL.
* Update stackato.yml MySQL service reference syntax and add ignores section.
* Ignore generated resources.