Qt: Only use GpgME based config class

* lang/qt/src/qgpgmecryptoconfig.cpp,
 lang/qt/src/qgpgmecryptoconfig.h: Removed.
* lang/qt/src/qgpgmebackend.cpp: Return newcryptoconfig.

The GpgME based config class is the way forward and the
old class was using KDE Code. Probably needs some bugfixes
as previously the new class was only used for Windows CE