use of exceptions instead of 'return None' + docstrings for the lib
update doc + remove the old KnownUser lib (the bot currently won't work until the new command for KnownUser is written)
fix warnings in doc generation
add LiveUser class and start the :user command implementation (only
tested in --interract yet)
new :user create method + an XMPP administrator can create new KU
Changes in user management:

    - add properties and hooks to access easily to live/db users
    - managers are now attributes of a bot
add __contains__ methods to do tests + simplification of unit test
create unit test for the CmdKnownUser + fix it
bugfix: automatically create a 'Chan' in the database when the bot joins a room