GitLab

Force the thumbnailer to stop when closing the window or
changing directory;  Kill the thumbnailer if it lasts more then
3 seconds;  Update the thumbnail icons every 250 msec instead of
every 20 thumbnails.

this is usefull to avoid a useless file loading when the
selection changes quickly

the file_tool is now a base class instead of an interface,
the toolbox is a notebook with the tool options.

The next step is to use GnomeDesktopThumbnailFactory instead of
GnomeThumbnailFactory, but I need Fedora 11 installed to test that.

Also, some logical fixes.

Something is still broken when plugging in camera, though. Something
weird in the gphoto backend, probably.