"Survey" feature units mismatch with MP in imperial

[iskess]

The Survey function only allows metric units. When it creates a flightplan and Mission Planner is set to imperial, the values stay the same but the units change which results in all values being in error. This is exacerbated by the fact that MP never shows what units it is using. This is very confusing and could be dangerous when 100m altitude becomes 100ft.

Ideally the Survey function would allow for imperial as an option.
The MP Flight Plan should display which units are selected for clarity.

[iskess]

This bug still hasn't been addressed.

[tristannovak]

@iskess
Check out Survey (Grid) after pull request #565 is committed, its not complete or perfectly idea, should be a good start though.

I still have to add support for speed...