Web Planner: Display coordinates of mouse pointer

Display the mouse pointer coordinates somewhere on the screen - e.g. in a text box in the top panel.

The coordinates to be Lat/Lon and, if available in future, followed by coordinates in the local system chosen by the user (e.g. OSGB36).

This is useful when plotting from a route description using coordinates and bearings, as well as general positioning/locating where you are on the map.

(Note: Several other Web route planners do provide this so it's definitely possible)