Adds tool option to align selected elements to the current grid. Fixes https://gitlab.com/kicad/code/kicad/issues/5481
Fixes https://gitlab.com/kicad/code/kicad/issues/5638 Fixes https://gitlab.com/kicad/code/kicad/issues/5588
This generalizes both the SetPosition() function and ORIGIN_VIEWITEM class away from the pcbnew-centric.