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
Add GeoPIxmapGraphicsItem
WIP: Port APRS plugin to GeoGraphicsItems