Bug 1023500 - [VsD Refresh] Lockscreen Visual Refresh > Notifications not to spec

Patch for 2.0 
I feel it's very improper to call lockScreen instance directly in another component. This coupling is too strong. I would suggest that we move these code inside `lockscreen.js` and `notifications.js` out to another file like `lockscreen_notifications.js` to do the same work, and fetch it's elements from DOM tree and communicate with these two components (if it's necessary) with some 'notification' or 'lockscreen-notification' prefix events.