Add notification to group chat rooms with ongoing conf calls

This notification disappears when in the conf call / when the call is over.
CSS stolen from the desktop notification bar.

skins/base/views/pages/MatrixChat.js

@@ -89,6 +89,7 @@ module.exports = React.createClass({
                 call_element = <CallView className="mx_MatrixChat_callView"/>
             }
 
+            // TODO: Fix duplication here and do conditionals like we do above
             if (Notifier.supportsDesktopNotifications() && !Notifier.isEnabled() && !Notifier.isToolbarHidden()) {
                 return (
                         <div className="mx_MatrixChat_wrapper">