Added Stellarium

Stellarium is a free open source planetarium for your computer. It shows a realistic sky in 3D, just like what you see with the naked eye, binoculars or a telescope.It is being used in planetarium projectors. Just set your coordinates and go.

I could not use the default SourceForge link style (I used the secondary one that goes to `downloads.sourceforge.net`) because the default "latest edition" download points to source code.