Handle @InheritanceType in a correct manner
If a model is extended the base class needs to be annotated with InheritanceType. Problem is that we don't know which classes will ever be extended, and Doctrine throws an error when the InheritanceType is set without discriminator map:
Uncaught Exception in FLOW3 Entity class 'F3\FLOW3\Security\Account' is using inheritance but no discriminator map was defined. thrown in file .../ORM/Mapping/MappingException.php in line 202
In such cases the annotation must be ignored by our annotation driver, or the IneritanceType should be set automagically if FLOW3 detects that a model is extended.
Relates to: https://review.typo3.org/#change,2130