Remove Control, Shift, Alt mappings and allow combination presses for each mapping#796

I understand why it’s currently set up this way, but being able to remap a mapping called Alt to something other than Alt is very confusing and weird. It’s to allow things like alt-previewing or alt-rotating objects but it’s a bad solution. Controls should let up map combinations of keys like “Alt+Q” and there should simply be a different mapping for each options currently affected by a modifier key.