[Qt] add utilitydialog.cpp/h and helpmessage class

- adds a nice and well formated dialog, which displays our -? help message
  (all options/paramaters)
- moves aboutdialog.cpp/h to the new utilitydialog
- move GUI shutdown window to utilitydialog

![helpmessagedialog](https://f.cloud.github.com/assets/1419649/1931502/13fdd45a-7ec0-11e3-868e-651c0b0dfe2a.png)