Highlight and scroll widget into view in preview window

When beginning to edit a widget or when hitting Update, the preview window should scroll the widget into view, or make sure it is in view. Likewise, when hovering over a widget control, the widget in the preview window should highlight with a red outline, and likewise when clicking on a widget in the preview, the corresponding widget control should expand in the customizer panel.

1. ![Hovering over widget for collapsed customizer section](https://f.cloud.github.com/assets/134745/1189934/8d8ea3f6-2427-11e3-8981-dbbfb889de63.png)

2. ![Hovering over widget highlights control](https://f.cloud.github.com/assets/134745/1189952/519528a6-2428-11e3-8f62-fe21e1e74aef.png)

3. ![Tooltip appears when hovering over widget in preview; click and section and form expand, with first element focused](https://f.cloud.github.com/assets/134745/1189949/11d4d158-2428-11e3-84f2-69787ce59159.png)

4. ![Hovering over control highlights widget in preview](https://f.cloud.github.com/assets/134745/1189976/46a7b426-2429-11e3-8334-a5c341bb296e.png)