#78 created static method HeadlessMapProvider.createHeadlessMapProviderAndAddLayers()
#82 HeadlessMapProvider: added an NotificationLevel UNLOCKED. Which is sent in unlock()
#82 HeadlessMapProvider.HeadlessMapProviderRetrievalListener added sendNotification(String, NotificationLevel, RetrievalEvent)
 #82 PrintWidget.startLoading() uses HeadlessMapProvider insetad of handling the creation of image of the map itself.
	Also minor changes: log -> LOG, Jalopy, imports
#82 Make us of NotificationLevel instead of self defined Strings
#82 PrintWidget implements PropertyChangeListener and does not implement RetrievalEvent anymore. Also added propertyChange()
#82 removed unused fields and methods of PrintingWidget