Add Notifications for messages and other events

[FrascoSal]

I suggest having notifications (bell getting red next to the profile nickname) for the following events:

• when an opponent clicks on the 'ready' button in a tournament game
• when an opponent proposes a date to schedule a match in a tournament game
• when an opponent sends you a message in chat in a tournament game before it starts (as supposedly it's to schedule the match, but once that game starts there is no need anymore for notification)
• 1 hour before a tournament starts or a scheduled game starts (reminder. Not sure about this one, definitely will be useful later on for live tournaments, but not necessary for tournaments with flexible scheduling or correspondence as we have them now).

For the future: enable email notifications