Generic App Icons: Part 3

I added two new generic icons: Music and Docs. You could use the docs one as a references program, but I still have a separate one in mind that I'll get to work on shortly (first I need to redo my whole icon file to bring it inline with upstream). Feel free to use either if you would like.
Merge pull request #27 from HalosGhost/patch-5

Generic App Icons: Part 3