Fixed view undo so that it returns to the exact previous point. Also allow view redo (with ViewBox default key "+").
Fixed view undo so that it returns to the exact previous point. Also
allow view redo (with ViewBox default key "+").

marinkaz/orange3,kwikadi/orange3,qPCR4vir/orange3,qPCR4vir/orange3,marinkaz/orange3,qusp/orange3,cheral/orange3,qusp/orange3,kwikadi/orange3,cheral/orange3,cheral/orange3,marinkaz/orange3,qusp/orange3,kwikadi/orange3,qPCR4vir/orange3,qPCR4vir/orange3,qusp/orange3,cheral/orange3,kwikadi/orange3,marinkaz/orange3,marinkaz/orange3,kwikadi/orange3,qPCR4vir/orange3,qPCR4vir/orange3,kwikadi/orange3,marinkaz/orange3,cheral/orange3,cheral/orange3