Add a MouseArea to the MapItemView delagate and onClick set
the "mapHelper.model.selectedUuid" to the uuid of the clicked marker.
This updates the "selectedUuid" property inside MapLocationModel.
Based on "mapHelper.model.selectedUuid" it is now possible to
show two seprate images for selected / deselected markers.
Signed-off-by: Lubomir I. Ivanov <neolit123@gmail.com>