new API for connection monitoring

Implementation of a new API allowing to monitor connections for Jami

1. getConnectionList(accountId, conversationId) returns connection information:

• IP/Port
• Connection state ( Waiting for DHT response, Ice, TLS, Connected)
• Contact (Contact Uri, Contact Device)

If accountId is empty => all connections for all accounts

If conversationId is empty => all connection for this account

ConnectionId = ptr of the MultiplexedSocket

2. getChannelList(accountId, connectionId) returns channels with specifi connectionId:

• Channels's Uri
• Channel's Id