Update DSO catalogs

[SevenSpheres]

This is unlikely to be done in the near future, so might as well open an issue for it. Celestia's catalogs of galaxies, globular clusters, and open clusters need to be updated at some point. This will require creating new scripts to generate them, and finding sources with all needed data (for galaxies, particularly a source of data from which Axis/Angle parameters can be determined).

A nebula catalog would also be nice, but that would require some major code changes since adding a bunch of nebula models to the default distribution would increase the file size too much.

[pedro-fixingstuff]

For globular clusters, maybe this source could be used: http://people.smp.uq.edu.au/HolgerBaumgardt/globular/. It might not have all needed parameters, but it's recent and comprehensive.

[SevenSpheres]

By now there have been updates to the globular cluster and open cluster catalogs, but not the galaxy catalog.