Prevent screw head z-axis translation while using the scale option

[luckychris]

if i create a screw head (which works with the update like a charm ;)), i can now choose the screw with my touchpad, but....a little it's a bit annoying that scaling "moves" the screw as well, if i offset it before:

[tristan-hm]

Good find. I've always naturally scaled them first, then moved them into position, so I've never noticed this issue before. I'll take a look at fixing it.