tracking changes works the way it is supposed to. Creates a TracksChangesEntityBase class for any other entity
that wants to implement IRememberBeingDirty (now Entity inherits from this). Upgraded a bunch of other entities that
were not tracking changes properly.
kept all properties, etc.. internal just so that they can be found so we don't have to register them.
Updates unit test to ensure the plugin manager is init'd properly with the 'false' override. Ensures that the base
db test also initializes the plugin manager properly.
Current checkin has a few new failing tests due to recent changes, but a few should be resolved by adding a DataTypesResolver setup in the ContentServiceTests fixture.
Adding the PropertyEditor model as internal to slowly adopt it using a slightly different model approach then in v5.
Minor refactoring of IEntity/Entity.
