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.
Refactoring base ContentType Repository and its implementations to allow for queries against PropertyType - still needs testing though.
Adding mappers for PropertyGroup and PropertyType models, so they are usable for queries.
