Specify the receiver of the message stream when the visibility is User or Group

Right now there is very little difference between the messages sent to Users or to Groups.

More, you can sent messages to users or group that don't exist. This means that if you entered a wrong username you won't be able to find out if the message was deliver successfully.

We should have a way to see where we sent that message in order to differentiate the stream and in order to be able to correct our errors.