Set up client basic architecture : receive thread, client state, conversation structure
Changed from IPv6 to IPv4 and added the correct ip instead of the dummy "ip addr" upon connection to dispatcher
Clients can now add and delete contacts from their contact list (it is persistent)
Fixed a bug where all contact lists were merged into only one (on a given machine) : now each user has its own contact list stored to file. Not yet encrypted, but this is the next step. Besides, adding and deleteing a contact locks the state so that multiple, quick addings or deletions of contacts is garanteed to result in a coherent state.