Add support for X/Y position before Z probe

[rsteckler]

My shapeoko (and I'm assuming pin 5 GPIO devices) have the z probe detector at a specific location. It would be great if the z-probe feature would auto-locate to that X/Y position before plunging. I'm guessing two new settings: Zprobe X position and Zprobe Y position.

Love the plugin. Thank you so much for supporting it!

[paukstelis]

I happened to be looking at probing when I saw this issue, so I took a whack at it. Not tested! Values are mm to jog (relative) before Z probing (should compensate for frame position). https://github.com/paukstelis/Octoprint-Bettergrblsupport/tree/xy_on_zprobe

[synman]

Hey @paukstelis ... not sure how far your fork has diverged, but I'm more than happy to take this as a PR.

Yeah, I know... 3 months to respond. I've been busy doing nothing else in particular these past few months.

[paukstelis]

Honestly, I barely even remember this 😄 . I know I have never tested it, which makes me somewhat hesitant to submit a PR, but if someone is willing to try it out I can.