Fully working phone call support, might need some tweaks and checks
Fixed 'call' method from jerbob92
Added command create_group_chat <user> <chat topic>.

Currently it supports only 1 user on creation.
Use chat_add_user to add more users to the chat.
Merge pull request #121 from vDorst/create_group_chat

Added command create_group_chat <user> <chat topic>.
Update loop.c