Introduced Arquillian-based example for JPA 2.1 custom converter feature

This project demonstrates following new additions to JPA 2.1
* Custom converter for `CreditCard` object which belongs to Employee
* JPA 2.1 schema generation / db seeding options (see `persistence.xml`)

In addition to Arquillian following tools has been used:
* AssertJ fluent assertions to verify the result of retrieving all objects from the datastore
* ShrinkWrap Maven resolve to bundle AssertJ with test deployment

I have removed derby from global dependencies, as it was leading to 
`java.lang.SecurityException: sealing violation: package org.apache.derby.impl.jdbc.authentication is sealed` when running on Glassfish Embedded. @arun-gupta please let me know if that is safe.