Removed unnecessary tabindex -1 from Video template.
For YouTube videos tabbing from Speeds to Volume closes Speeds dialog.

An old TODO item was done. It turns out a simple case of calling
the method to bind handlers after the Spees dialog was re-rendered.
Fixed tabbing backwards.

Now you can tab through all of the controls in Video forwards, and then tab backwards.
Adding documentation to the event handlers for volume and speed control.