Add value change listeners to the Record Object

[Ryan How]

Hi Lukas,

What do you think about bloating the UpdatableRecord object a bit more and 
adding value change listeners to the record?.

My use case is that I am using the UpdatableRecord for data binding 
purposes. It would be great to listen to value change events in the record 
so I can then sync back to the UI.

This UpdatableRecord object is like a swiss army knife. I love it :)

Thanks, Ryan