Documenting the Downloads Folder

[David Siegel]

Hi docs team!

With https://bugs.edge.launchpad.net/hundredpapercuts/+bug/204567,  
downloaded files now go to a "Downloads" folder within the user's home  
folder, with a bookmark for "Downloads" in the Places menu and the  
Nautilus Places sidebar. I was unable to find existing documentation  
for working with downloaded files, but this change may warrant  
documentation. Perhaps it could be added to documentation explaining  
the default XDG user directories for pictures, videos, documents, etc.  
if it exists?

Thank you,
David Siegel