* src/ntl-view-bonobo-control.c: In notify_location_change, send
progress back (because the Bonobo control, which might be the
content view, can't do it).

* src/ntl-view-bonobo-subdoc.c: As above, plus don't use
PersistFile interface, plus use bonobo-stream-vfs instead of
bonobo-stream-fs.

* src/ntl-uri-map.c: If no content type is found, default to text/plain.

* libnautilus/bonobo-stream-vfs.[ch], libnautilus/Makefile.am:
Initial implementation of bonobo streams in terms of Gnome VFS.