Make coordinates recorded during drawing conform to geojson

[defiantgoat]

Currently, when a user draws on the map the coordinates are stored in an ad hoc application only type of array structure. Would be good to revise this to match a geojson spec so that it geometry can be saved out later for use in other scenarios if necessary.

[defiantgoat]

QML Map Polyline looks for an array of objects with latitude and longitude property names, so this doesn't actually make sense to do. However, the application could have a function that outputs geojson from a drawn extent or polyline.