download-dir setting not being respected

[Xan Lopez <xan gnome org>]

With the download rewrite in ephy we stopped following some of our
documented behavior in the download-dir key. In particular,
"Downloads" is no longer understood to be the downloads dir, and we
use the desktop directory when the key has that value. Patch in
https://bugzilla.gnome.org/show_bug.cgi?id=644641 rectifies this.
Permission to commit for 3.0?

Xan