QtProtobuf: address namespace issues

Currently the QtProtobuf module (WIP) cannot build properly with a namespaced build of Qt. The library is properly built with namespaces but the Qt*-types are not and cause failures due to ambiguity. This is because the main library and the generated types are both in QtProtobuf, but the generated types don't apply the Qt namespace.

We can either find a solution to apply the Qt namespace to these types or we can find an alternate namespace for the generated types.