Mapbox: Add events for Draw polygons/lines

[erictuvesson]

In the Mapbox module you can draw polygons/lines etc.

This is something that have been attempted to be supported by the module to make it easier. It is something that has to be improved even more to make it a more viable solution instead of just writing some Javascript next to the node.

A first step would be to get some extended information when a new object is added by the Mapbox draw tool.