Code review comment for lp://staging/~gary/juju-gui/databindingChangedValues

*** Submitted:

improve databinding changedValues accuracy

- more accurately keep track of changed values
- switch changedValues to being an Object
- Make changedValues public
- added eq to databinding fields

R=rharding, benji
CC=
https://codereview.appspot.com/13385045

https://codereview.appspot.com/13385045/