Blender Git Loki

Bug #2839: Shift key not working in Shear, Push-Pull and shrink-Fatten

- I changed the input method for shear quite a bit. It used to be constant
regardless of zooming, so it was quite limiting in the amount of shear you
could do. However, I'm not sure if the current method is quite well
adjusted, if you think it works too fast, please drop me a line.
It's basicly the same method as Shrink-Fatten / Push-Pull except on an
horizontal basis. (since shear is an horizontal motion and the two others
are more like pulling towards/pushing away from you in regards to the center)
- Factored out the input methods in preparation for later code <evil>.