JPACacheStore should be able to lookup a container manager Persistence Unit

The current JpaStore implementation starts all its EntityManagerFactory instances by using the Java SE recommended method, but this has several limitations:

• it's likely a duplicated persistence unit as the container will start one as well
• duplication leads to name clashes and lack of statistics in dashboards
• the container won't inject special features, such as the appropriate JTA context
• custom extensions from the container, like on WildFly you get a better scanner
• better integration with datasources
• Infinispan does a poor job in managing the lifecycle of its custom starte PU (not shutting it down)
• several containers apply some customizations to get Hibernate to work best (or at all) on them, you'd bypassing these compatibility fixes