Pervasive GSF use

As you may have noticed, a lot has happened with respect to
import/export filters in the past few hours. Here's a status update
for those of you who don't want to read all of the commit emails:

All of the import and export filters use libgsf now, which means that
they work again (well, as well as they ever worked). This means that
they can read and write remote files, read and write images to/from
remote servers, etc. The sole exception to this is the PDF exporter,
which won't save files remotely (because it uses gnome-print). This
will be fixed when we create a Cairo graphics class. This also means
that we get some niceties from libgsf, like not corrupting a
previously saved file if a subsequent save failed.

Also, a few nit-picky bugs in the file chooser wrt URI handling have
also been fixed.

This all needs a ton of testing. It seems to work ok from the Unix
file chooser, Unix command line, mail merge dialogs, clipart dialogs,
and etc. I have no idea how well things work on Mac and Win32, but it
should just be a matter of adding a few UT_go_filename_to/from_uri()
calls at interface points, like the file chooser. Otherwise, all of
the grunt work is already done.

Enjoy the new (now functioning) feature,
Dom

-- 
"I believe in making the world safe for our children, but not our
children's children, because I don't think children should be having
sex." -Jack Handy