added 2 functions:
def list_users_in_role(role):
"""List all users of a given role (see table accROLE) @param role: role of user (string) @return list of uids"""
def list_users_in_roles(role_list):
"""List all users of given roles (see table accROLE) @param role_list: list of roles [string] @return list of uids"""