[C++][Qt5] Rewrite of Qt5 Code Generator

The Code generated by the qt5cpp generator is incomplete and does not really match the other client library structures ( like cpprest, perl, ... ).

I would create a complete new set of templates and adapt the generator code, to make sure, the Qt5CPP generator behaves like cpprest and is more feature complete.

Is there any active maintainer for Qt5 or such a project already in progress?

As there is also #3203 outstanding for Qt5 i would also take care of this.