Removed notification timer from ChatView
Added new chat message notification noise and licensing information for the sound file. Removed old public and private notification sounds and the relevant code. Commented out code from the old timed notifications.
Added logic to determine whether or not to play the notification sound. Sound now plays whenever a message is received, like many other chat clients.
Removed commented code pertaining to the old timer-based notification system.
Chat tabs now modify their accessibility description to tell a screen reader whether there are new messages in that tab or not. Removed logic pertaining to ChatAccessibilityEvent, which was introduced as part of this branch and is no longer needed.
Still experimenting with ChatTabs accessibility.
Notifications in chatTabs are not working. This bears returning to later.
Resolved conflicts
Merge pull request #203 from SenecaCDOT-BigBlueButton/chat-access-notification

Chat access notification