GUI overhaul

This is an overhaul of the GUI code, changes include:
* Using KSP's "skin"
* Remove manual window resizing code, utilize automatic resizing. 
* Fixes the "SAS Presets" window not disappearing when "SAS Module" window is hidden. 
* New design, overall hopefully a better GUI. 

Basic testing done, however there may still be issues of course, please don't hesitate to let me know of any bugs/issues.