add a new MapProjection implementation (OrthographicAzimuthalMapProjection)
improve HackMapProjection and make it reversible
improve MercatorProjection code quality
add debug views for internal coordinates and lat/lon
merge master

Conflicts:
	src/org/osm2world/core/ConversionFacade.java
	src/org/osm2world/core/map_data/creation/HackMapProjection.java
	src/org/osm2world/viewer/view/ViewerFrame.java
use TagGroup and MapElement convenience methods to improve code
remove unused VectorXZ.distanceFunction
make map projection configurable in ConversionFacade, extract origin calculation
merge new projection implementations