JPAFacet.getAllEntities should not expect JPA entities to be present in a predefined Java package

AbstractJPAFacetImpl.getAllEntities() relies on the JPA entities being present in the same package in a project with the JPA facet. Additionally, it expects the package to be named "<groupId>.model".

The REST and Scaffold addons therefore depend on the JPA entities to be present in this package, failing which no entities are displayed to the user.