add guest list command to get all users of a given host leitzahl

allow adding users (aka personas) to persons (aka users)

optionally do not change the initial passwords of a guest user

made date conversion Windows compatible

added init-passwords for guests and users

fixed notification bug when updating guests

added pytz to setup.py

added python-dateutil to requirements

added support for guest and groups via CLI

added __getitem__

added Mailbox service managment, password management and password check

changed order of params in login function

improved error message, implemented alternate URL

added support for extra host

added AD password reset support

fixed dependency list

added more CLI support, including setting passwords

added support for creating groups

optimized CLI for better help and lazy username/password prompt

added small CLI for group management