Use debugfull configuration whenever it is available.

Esp. with newer FindKDE4Internal.cmake files this configuration is
also available for Clang and required there. As soon as any function
gets inlined, our unit tests would fail otherwise...
Revert "Use debugfull configuration whenever it is available."

Apparently this is unsupported, see:
http://public.kitware.com/Bug/view.php?id=14634

This reverts commit 56044bcbe5b0e9e19fd83995563e31fdd4cde222.
Use the add_debuggable_executable macro everywhere its required.

Apparently that is more reliable than setting CMAKE_BUILD_TYPE
in a subfolder. See also:

http://public.kitware.com/Bug/view.php?id=14634
Minor code cleanup
Fix regressions introduced by recent refactoring.

Fixup signal connection to use fully qualified ID.
Take correct type out of variant.
Reduce QVariant usage.
Make compile for me