Use the new "no_use_remotemounts" and "use_remotemounts" tags,
because those are more descriptive.
Do not setup ~/"${schooldir_displayname}" and ~/"${userdir_displayname}"
links for laptops in puavo-update-gtk-bookmarks, if there are no
remotemounts.
Remove "exit 0" that should be never reached in puavo-remotemounts-helper.
Convert puavo-remotemounts-helper to ruby so that different
mount monitors can be neatly run in their own threads.
(I feel I don't like the shell-way of doing threads).