Rotation for Full Screen Dashboards

We've added the ability to rotate full-screen dashboards. This allows you to show your dashboard on a vertical external display using a Chromecast or Apple TV. For example, here's a full-screen dashboard with the following URL:

When you click the "90°" button, the URL changes to

This is rotated on your computer, but when you take that URL and display it on a rotated TV, it looks like this: