Mouse coordinates format should be multi-map aware

[jumpinjackie]

Load any multi-map appdef whose maps coordinate system's are based in different units and the mouse coordinates will apply the same label for both resulting in non-sensical things like:

Lon: some other meters-based value, Lat: some other meters-based value deg

To fix this, we need each map in a multi-map configuration to carry an optional label override and this component should use the override for the active map if present before falling back to default label formatting behavior.