New Compass ordering screen

[rmackay9]

While reviewing's @bugobliterator's compass ordering PR ArduPilot/ardupilot#12629 I also tested MP's new screen. Overall it's a good looking screen but I quickly found several issues:

• does it really support 8 many rows? We don't have this many parameters in AP so I can't see how it could
• row highlighting:
  • checking on the top "Set" column colours them all but it's not clear what this is for
  • if the user can't modify individual fields, maybe it would be better to have the whole row light up
  • why highlight a row at all?
  • if multiple rows are selected, I might then expect the Up/Down buttons to affect both rows but it doesn't. I'd remove the ability to select multiple rows.
  • a more common method is to have just two up/down buttons that affect the highlighted rows
  • disconnecting the board and then pushing the up/down buttons causes a scary error message to appear
• reboot required message issues:
  • moving away from the screen caused a "Reboot required" message to appear but the flight controller was disconnected. This message box appeared every time I moved off the screen no matter whether I answered "yes" or "no"
  • reboot required appeared again when I clicked on the flight data screen even when I wasn't looking at the compass screen anymore and I'd already said "yes" once and the flight controller wasn't even connected
  • I think it would be best to get rid of this pop-up completely and instead add a "Reboot" button below the "Compass Priority" table. Perhaps change the colour of the button if the user changes the table in a way that means a reboot is required.
• similar to this other issue re the HW ID page, it would be nice to get rid of the "BUS_TYPE_" prefix for the values appearing in the "BusType" column
• "compass's" should be "compasses". Perhaps we should replace "moving around" with "reordering".

[rmackay9]

I'm slightly confused at how the Compass Priority section doesn't exactly match the COMPASS_PRIOx parameters even after I've restarted MP.

[rmackay9]

We got a request on the Copter-4.0.4-rc1 beta testing thread that requests the first column on the left have numbers 1,2,3,4,5,etc