GraticulePlugin: Port to GeoGraphicsItems
factor out ScreenLayer from GeometryLayer
wip idis
GeoGraphicsScene
always create a canvas image in texture mappers
GeoPainter::mapTexture()
const'ify
remove ViewportParams parameter from MarbleGraphicsItem::paintEvent()
const'ify changeViewport()
split GeoGraphicsItem::paint()
remove customPaint()
WIP: split LayerInterface::render() into paint() and setViewport()
deactivate to-be-ported RenderPlugins
Use line width from line style

* Set pen with for lines from line style if available
  in GeoLineStringGraphicsItems
Allow for icons in icon style

* If an icon is set in icon style for a GeoPointGraphicsItem
  draw it at the point's position
Add font setting to MarbleGraphicsItems
MeasureToolPlugin: Port to GeoGraphicsItems
GraticulePlugin: Set default grid alignment to Corner

* This setting lets the plugin behave more like it did before
  the port to GeoGraphicsItems
Add GeoTextGraphicsItem and GeoRectGraphicsItem
Use QPixmap instead of QImage in GeoImageGraphicsItem

* This changes GeoImageGraphicsItem to use a QPixmap internally instead
  of a QImage. GraphicsItem classes are for rendering and QPixmap is
  optimized for this purpose whilst QImage is not.