factor out ScreenLayer from GeometryLayer
fix
wip idis
GraticulePlugin: Use GeoGraphicsItems for rendering the grid
Allow for settings a font in MarbleGraphicsItems
Allow for icons in icon style

* If an icon is set in icon style for a GeoPointGraphicsItem
  draw it at the point's position
MeasureToolPlugin: Port to GeoGraphicsItems
Add GeoTextGraphicsItem and GeoRectGraphicsItem
Add GeoPixmapGraphicsItem
WIP: Port APRS plugin to GeoGraphicsItems
drawRect --geoProjected
drawEllipse --geoProjected
AreaAnnotationGraphicsItem
remove convenience variables
--drawPoint(s)
--drawPolygon()
--drawImage
--drawRoundRect
wip --drawText
wip remove GeoPainter::drawPolyline