Support multiple memcached servers (not implemented in the web interface yet).

s/dictionnary/dictionary/g
Fix property name begining by _v_ where not needed.
Raise an error if key is not a string.
Raise KeyError in __getattr__ when a None is returned by python-memcached.
Add try/except in _finish to be sure not to raise any error.


git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@11669 20353a03-c40f-0410-a6d1-a30d3c3de9de