GitLab

Show the text and the progress in the browser statusbar.

do not update the file each time a file_changed signal is emitted
to avoid  excessive file reloads

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.