Changes:
* Pass toolGroup into tools instead of toolbar
* Split tool labels into title and accel
* Make toolbars provide accelerator labels
* Remove getLabelText method since it's not being used and is likely not useful
* Make tools update their own labels
* Only show accelerator information for triggers that are active in the surface
* Make surface toolbars listen to commands being added and update tools accordingly
* Introduce command object to encapsulate command info
Change-Id: Ieac4bfa63b63ac0a9dee154af3007a33b4d447ff
