ISIS-553: view model support

* container.newViewModelInstance(SomeClass.class, "id")
* ViewModel interface (replacing @ViewModel annotation)

related
* support for @PersistenceCapable(identityType=NONDURABLE)
  eg as per http://www.datanucleus.org/products/accessplatform_3_2/datastores/rdbms_views.html

also:
* MandatoryFromJdoColumnAnnotationFacetFactory (as a metamodel validator)
  - no longer raises a violation for entities without the @PersistenceCapable annotation
  - does not raise a violation for NONDURABLE entities
  - does not raise a violation for properties with JDO @NotPersistent annotation