also corrected the "useSystemOnScreenKeybard" to
"useSystemOnScreenKeyboard".

- Corrected and cleaned up rotation calculation
- Fixed button position/size issues (clickable area didn't correspond to the button image)
- Fixed tool flashing during resizing
- (new feature) Buttons now scale proportionally to the protractor when it is resized
- Everything is now drawn by default at a scale of 1 instead of 1.5
- Pen width set to 0 (i.e always 1 pixel thick regardless of zoom), to keep the old look & feel
- Scaled the marker tool image (.svg) to look like it did before without scaling it in code
- Removed debug messages

Tested on OS X, works fine.