From the shortcuts pane, focus the GtkEntry and redirect unhandled keystrokes to it

From the shortcuts pane, focus the GtkEntry and redirect unhandled keystrokes to it

This lets us do this:

1. click on a folder in the shortcuts pane
2. start typing a filename

Then, the typed filename will actually go to the filename entry, like
the user expects.  (Or to the search entry, in case the user clicked
on the Search shortcut.)

Also, removed the obsolete callback that made "/" and "~" typed in the
shortcuts pane bring up the location entry.

Signed-off-by: Federico Mena Quintero <federico@novell.com>