Shows notifications upon success or failure of save and delete objects

[natanrolnik]

This PR enables the functionality we had in the original Parse.com dashboard (before the redesigned one) and closes #715

When a save/delete succeeds or fails, it will display a small notification for 3 users. I didn't write any new functionality, I only fixed/extended the Notification component.

It doesn't handle additions to and removal of relationships, but it does handle:

• Saving new object
• Updating existing object
• Deleting object
• Failure when saving object
• Failure when deleting one or multiple objects