stop using deprecated aliases of TestCase methods.

see http://docs.python.org/2/library/unittest.html#deprecated-aliases
rewrite anonymous support in selection.

* now Selection for anonymous is stored per its content and its key is embedded in ListBox rendering.
* we no longer provide cookie to each anonymous user.
* thus same URL (i.e. same parameter) for any anonymous user should have the same result.
* Selection storage for anonymous can be still different from the storage for the normal users.