Add command for memory position and move to x y z in memory

I use it when I change the filament automatically with the g-code change tools in Slic3r.
I have 4 extruders but a single nozzle, when I change the wire, move the nozzle out of the plane to make bleeding the nozzle. So before I memorize the position, I move to purge, and then resume from the last position.