allow custom scoped persistence unit name hint in persistence unit definition

Consider allowing applications to override the scoped persistence unit name, so instead of using names like "test2.ear/w2.war#warPUnit_PU", the application can specify a unique (across all deployments on the app server) name.

The idea is that application deployments can include a persistence unit hint "jboss.as.jpa.scopedname" that specifies the unique scoped persistence unit name that will be used for several internal settings (e.g. hibernate.cache.region_prefix will be set to the scopedname value unless the application specifies a different hibernate.cache.region_prefix value).

The WildFly management console does not yet work with applications that specify the jboss.as.jpa.scopedname. Once this change is merged to WildFly, a management console change should be requested.