sessions are indexed by id and time (last used time)
changed: old sessions are deleted
parameter: session_max_iddle in the config file
added: function 'who'
git-svn-id: svn://ttmath.org/publicrep/cmslu/trunk@483 e52654a7-88a9-db11-a3e9-0013d4bc506e
changed: item.url_subject into item.url
changed: a new table: content
with: id, subject, content, content_type
(those from the item table)
it helps to create hard links
git-svn-id: svn://ttmath.org/publicrep/cmslu/trunk@466 e52654a7-88a9-db11-a3e9-0013d4bc506e