[x] For XDG_CURRENT_DESKTOP=KDE keep the use of KFileWidget
[x] For XDG_CURRENT_DESKTOP!=KDE (e.g. XFCE) use the new Kexi's simplified file chooser
- done in ae36985459d6e94 using KexiUtils::isKDEDesktopSession()
[ ] Add setting to force the use of KFileWidget even for XDG_CURRENT_DESKTOP!=KDE or Kexi's simplified file chooser for XDG_CURRENT_DESKTOP=KDE. Default value should be as described above.