Add support for @PersistenceContexts and @PersistenceUnits

@Stateless
@PersistenceContexts({
    @PersistenceContext(name="OrderEM"),
    @PersistenceContext(name="ItemEM")
})
public class OrderEntryBean implements OrderEntry {
    @Resource EJBContext ctx;
    public Customer getCustomer(int custID) {
        EntityManager em = (EntityManager)ctx.lookup("OrderEM");
        return em.find(Customer.class, custID);
    }
    public void enterItem(int orderID, Item newItem) {
        EntityManager em = (EntityManager)ctx.lookup("ItemEM");
    ...
    }
}