new "archive" function -- and bookmarking feature in "$ edit"

# The 'edit' with bookmarks magic

I'm really excited about the idea to put bookmarks in custom/FILES
and have $ edit open it when called without argument.

Thanks for crafting bash-it, I would never have tried this without it.


# The 'archive' command

In its essence, the archive command does this :
  archive /tmp/TEST.png
  mv /tmp/2013-10-20--TEST.png

I follow here the principle that does wonder on gmail that, 98% of the time, archiving is better of deleting.

XDG Base Directory Specification
http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html


Please review this patch, I'm not a bash programmer.