Use x() and y() coordinates of ImageLayer when rendering to a QGraphicsItem
Add position property to ImageLayer. Include temporary values in constructor
Change MapScene to use position rather than x,y
Add position property to the propertybrowser for ImageLayer
Add position to ChangeImageLayerProperties for undo and redo commands
Add ability to set ImageLayer position in the property browser
Add ability to write position to file in mapwriter.cpp
Add ability to read position of ImageLayer from mapreader.cpp