[Notification][Linux] Add libnotify to the build package.
[WIN] Make StatusTray class a singleton, add a public function to get the StatusIcon, this is done to fix crash in notification manager trying to create StatusTray that already created by javascript api.
Change DisplayBalloon return param to bool.
Implement more BalloonEvent dispatcher for windows (Show, Hide, TimeOut).
Merge pull request #12 from jtg-gg/notification

Windows Balloon Notification