Feature Request: Add a plugin or capability similar to MagFit Tool

[hendjoshsr71]

Issue details

An equivalent to MAVExplorer's Magfit Tool should be created. Mission Planner is a far better tool for the normal user to interact with.

https://ardupilot.org/copter/docs/common-magfit.html?highlight=mavexplorer#using-mavexplorer-s-integrated-magfit-utility

I think this would likely be a plugin at first. (I'm mostly creating an issue to remind myself to do have a try at a plugin later.)