Some code written for new group chats.
Removed groupchats from core.
Removed now useless atributes from structs.
Update avatar documentation

Update the documentation to reflect the API changes introduced by
commits 21be438b2b3f7aa1b65b76a7f528eacfe5b634db and
d409bad30dd1657f6b54ea5e38a4d9155f718ae1
More groupchats code written.
Group chats are starting to work.
add API function to unset avatar
DHT can now be used for group chat cons and friend cons at the same time.
Wrote more new groupchats code.
Added callbacks to DHT called when the ip of a peer is discovered.
Removed now useless network sturct size tests.
Added callbacks to onion_client and net_crypto for the temp dht key.

Better than the polling mess.

Moved DHT to Messenger from onion_client (still needs some cleanups).
Removed useless code from onion_client.

Astyled.
Moved cleaup_friend functionality to Messenger.
Only set dht public key and direct ip when first creating connection.

Check if ip family is valid in set_direct_ip_port() function.
Remove timestamp from set_connection_dht_public_key().
Make the ip port from DHT timeout after a while.

Some small fixes.
Moved all the connection stuff from messenger to friend_connection.

Messenger was doing way do many things.

friend_connection takes care of finding and establishing a connection
to friends.
Increasing max number of onion paths might increase initial connection
speed.
Removed useless code from groupchats.