added dropdown for selecting map layouts to toolbar

...to replace the no longer working (Eclipse Luna) dynamic contribution
of layouts directly to the toolbar.

Change-Id: Iaef37bc9abc7aba007b4c0d5cc18eac9c6ae7fb9
Reviewed-on: http://gerrit.esdi-community.eu/3161
Tested-by: Jenkins <sitemple@igd.fraunhofer.de>
Reviewed-by: Simon Templer <simon.templer@igd.fraunhofer.de>