changed location of logo
removed loading of attributton
Revert "removed loading of attributton"

This reverts commit 51601899919539cb780ea786fc6c4d85cb0670da.
added factory which requires a api key; renamed BingTileSource again, since it is a specialized subclass only for images; changed attributon image: it is loaded in a factory and set in the tile source; extended test for map pane; fixed copyrights for BingAerial