reposition and move on screen controls 

Implemented a way to reposition on-screen controls.
It's still a little rough around the edges, but it's functional. Some UI polish is needed. 

I had to add another .cpp file. I think I've covered all the bases but I may have left the file out of build systems I'm not familiar with / don't use (Visual Studio and XCode). 

Also, I'm not sure if I've used the correct coordiante system (dp_xres and dp_yres for maximum screen coordinates). If they're not right, do tell me :)


Screenies:
The area where you can move the on-screen controls around
![screenshot_2013-10-11-20-59-18](https://f.cloud.github.com/assets/1694861/1316095/6b46e110-3290-11e3-8a73-a11894cab4cf.png)
![screenshot_2013-10-11-20-59-38](https://f.cloud.github.com/assets/1694861/1316096/6ba74ce4-3290-11e3-9c5b-64dd3853024e.png)

In-game:
![screenshot_2013-10-11-20-59-52](https://f.cloud.github.com/assets/1694861/1316098/704d71d8-3290-11e3-8185-d3f3c803a942.png)
![screenshot_2013-10-11-21-00-19](https://f.cloud.github.com/assets/1694861/1316099/704e2c22-3290-11e3-8fad-735269fbf269.png)