Added Controlbar to UI

Added the control bar described in this [document](https://docs.google.com/document/d/1meXJaS1OdkrvC4-veCE4w5o9O9pP0tHO-7PsIzHTCt0/edit?usp=sharing), it adds menu space for new features such as the highlight tool. It also resolves [issue 528](https://github.com/hypothesis/h/issues/528)

The interface looks like this when you hover over the speech bubble:
![controlbar](https://f.cloud.github.com/assets/521978/839254/50c01100-f33d-11e2-9557-48b04f243c33.jpg)