Ability to set the icon and actions for Notifications

[abishekrsrikaanth]

The current Notification class doesn't have a way to set the icon for when a Notification is triggered. It would be great to have a method setIcon() to the Notification class to do this.

In addition to this, it would also be great to have actions on the notifications. Right now there is only option to setup an event when the notification is clicked, but certain apps are able to setup actions on these notifications and add behavior to those actions.