Autodetect Beacon for homing z

[Zeanon]

Automatically detect beacon for z-homing (like autodetecting sensorless homing) and set the appropriate settings by default to make sure users who dont read the doc fully dont put in wrong settings and to clean up the config/make it easier for everyone else

Checklist

• [x] pr title makes sense
• [x] squashed to 1 commit
• [ ] added a test case if possible
• [x] if new feature, added to the readme
• [x] ci is happy and green

[rogerlz]

looks good to me.. would you please add a comment to the config reference about this change too?

[Zeanon]

Closing it for now as I have to figure out a more reliable way of doing it with dalegaard