Add Shift modifier to spacer tool to move guides too #702

Relatet to #702 (closed)

If you press Shift while using the spacer tool it affects guides to.

Known limitations: At the moment you do not see the movement of the guides in real time. They are just moved when you release the mouse button. Personally I think its not that worse but seeing the movement in real time would of course be nicer. I am not able to deal with this challenge. Maybe someone else does or can guide me. But like I said: for me the MR is already useful in its current state Demo