Embryon functionnality for snapping. - Only snaps to grid on translations (grab) - Transform constraints are supported but header display is wrong. - Can be turned on/off in the Object/Mesh header menu under Transform Properties (tentative spot, will have to integrate better and in other object type menus too) - Can be turned on/off during transform with ` (Back Quote, also tentative) This is, of course, very much Work in Progress. This implements part of the structural ideas for the transform cleanup I've been juggling around with.