feat(ionNavBar): use declarative syntax

Closes #777 
Closes #596 
Closes #477

- http://ajoslin.github.io/docs/nightly/api/ionic/directive/ionNavBar/
- http://ajoslin.github.io/docs/nightly/api/ionic/directive/ionNavBackButton/
- http://ajoslin.github.io/docs/nightly/api/ionic/directive/ionNavButtons/

Also: +25 or so tests :-)