Add a change bar based on content status

instead of special-casing `draft` and `publishing` add a changebar (and labels) if a status is set (publishing is blue and draft is yellow). This also simplifies the logic for the case when content is in the `publishing` state.

Screenshot (draft Book and Page):
![image](https://cloud.githubusercontent.com/assets/253202/2868172/b8b56902-d241-11e3-8944-5d15feeaa48c.png)



Screenshot 2 (just draft Book):
![image](https://cloud.githubusercontent.com/assets/253202/2868184/e63aeaa0-d241-11e3-974b-da3aaa82520b.png)



TODO:

- [x] add "draft" labels next to the input boxes (they are hidden because of `editable.coffee`