- Use simple approach to data dir. Current setup of code not allows both

 - Use simple approach to data dir. Current setup of code not allows both
  qt4 and qt5 cohexists, and data files are same for both libraries.
  If a different data dir is required for specifics reason, is possible
  to set in cmake run -DLXQT_LIBRARY_NAME:STRING="string"

Signed-off-by: Helio Chissini de Castro <helio@kde.org>