Snap surface move to angle.

[rukai]

Ctrl + Shift + Alt are already taken as surface type modifiers, ideally we would use them here but maybe we will need something else.
Hold Shift to snap the currently moving surface to 0, 22.5, 45, 67.5, 90 ... degrees

Alternatively:
We could have a button angle-snap selected surface sides in line to its opposing side.
This means we dont need to free the shift key.
Would have some weird, potentially unintuitive/unhandleable, edgecases.