add notification in tab + improve unread message notification

[Incubatio]

Currently when receiving a text message, if connected to the client, user will receive a sound notification.

However if the user doesn't hear the notification (because not in front of computer or music is too loud), he might miss the message.

Sending a mail for each text message could be a solution, however it would be unpractical for intensive texting (flooding mails).

A better solution could involve:

• Sending mail containing the digest of new unread text message every hour.
• Also adding visual notification in the browser tab (favicon).