Fix for various naming collisions

This should fix https://github.com/dart-gde/discovery_api_dart_client_generator/issues/32 and https://github.com/dart-gde/discovery_api_dart_client_generator/issues/33 and some other potential collisions that might appear in the future.

@damondouglas @financeCoding can you checkout my fork and see if the dart analyzer still complains for you?