Improve SeesionTool to work as well in a distributed environment (memcached, MySQL).

Make use of already present cache plugins used as a storage.
Extend test to cover functionality for all kind of storage (i.e. cache) plugins.


git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@24702 20353a03-c40f-0410-a6d1-a30d3c3de9de