Changeset 605 for trunk/random.php

category random replaced by a more generic category : list. You give a list
of element identifiers and it creates a page virtual temporary
category. random.php generates a randomized list of element id visible to
the user (according to permissions) and redirects to category.php.

Major problem : elements order is in id ascending order, I don't know how to
change order when having id1,id2,id3 and id2,id3,id1 (the display order is
the same)