Label: Add class documentation

	* Add documentation block for Label class.
Location: Create new Location interface

	* Add declaration of Location interface.
Marker: Update to latest 0.12

	* Remove get/set_highlighted(), set_position() methods.
	* Remove highlighted, latitude, longitud properties.
	* Add get/set_selectable(), get/set_draggable(), get/set_selected()
	methods.
	* Add selected, selectable, draggable properties.
	* Add button-press, button-release, drag-motion, drag-finish
	signals.
	* Add documentation.
	* Add implemented interface Location.
	* Create marker.ccg