Should contain code that creates all the neccessary DOM elements for the
control, adds listeners on relevant map events, and returns the element
containing the control. Called on map.addControl(control) or control.addTo(map).
Optional, should contain all clean up code (e.g. removes control's event
listeners). Called on map.removeControl(control) or control.removeFrom(map).
The control's DOM container is removed automatically.
Should contain code that creates all the neccessary DOM elements for the control, adds listeners on relevant map events, and returns the element containing the control. Called on map.addControl(control) or control.addTo(map).