Marble: Add labels in the stars plugin for DSOs
completed by: Timothy Lanzi
mentors: Torsten Rahn, René Küttner, Dennis Nienhüser
The stars plugin should show labels for the DSOs. The labels should show the catalog number (e.g. M44) in the color aluminiumGray6.
Additionally please add NGC 5139 (Omega Centauri) http://en.wikipedia.org/wiki/Omega_Centauri to Marble's dso catalog.