Adds several new open-xxx() functions.

- open-bin,
- open-documents,
- open-downloads

These are folders that I put into my speed list in Dolphin so I
thought I should make them more accessible when I'm using Emacs,
especially since I use Emacs more than I use Dolphin.

Some folders like Music, etc. don't need to be there because I don't
really go there using Emacs . . . yet.
Changes uag.org to uag-tasks.org