Virtual modes with scale and panning. Brightness control

Hi,

I have just done some changes in Lxrandr-qt. I added:

- Virtual modes with scale and panning.
- Brightness control.
- Xrandr mode lines are read using libxrandr instead a pipe to xrandr 
command. I use some code from xrandr.c

There is a screenshot in:

https://drive.google.com/file/d/0B1x9hVRJS4GmUndZRGtDQ2Y1VWM/edit?usp=sharing

Virtual modes let you select modes bigger than your screen ones. Either 
screen images can be resized or you can move through your virtual screen 
(panning).