Add more projections

[nighthawk]

An issue to collection various map projections that might be worthwhile to add:

• Aitoff

• Danseiji. When support is there for one, then that should cover all of them via the different input files.

• Eckert IV

• Mollweide

• Natural Earth => Add NaturalEarth projection #35

• Robinson

• Wagner VI

• Web Mercator => Would just be a slight tweak of the existing Mercator, trimming it at the same bounds.

• Winkel tripel, as used by the National Geographic Society