IdentityService changed to IdentityManagerService

I've renamed IdentityService to IdentityManagerService. Instead of Service<IdentityService> it now provides Service<org.picketlink.idm.IdentityManager>, and the IdentityManager is also bound to JNDI.

Instead of providing an EntityManager producer, it now provides an IdentityManager producer.

I also added a dependency on the datasource (hardcoded to ExampleDS for now as the persistence.xml is hardcoded to ExampleDS).