Feature: Rotate image axis

I have another feature request. When taking photos with a Ricoh Theta camera, they contain ZenithX, ZenithY and Compass data in the exif so the viewer can auto-level the horizon if the camera wasn't held 100% vertically during the shot.
Could you add support for the Zenith data as extra parameters?

You can find some details on these (japanese) pages
http://like.silk.to/theta360/zenith.cgi
http://xanxys.hatenablog.jp/entry/20131110/1384094832#20131110f1

The Ricoh Theta windows app can also auto-level the orientation and write a new jpeg file but since that is a lossy operation, I'd prefer it if the rotation happens in the viewer.
Perhaps it's just a matter of applying some transformation once when you create the ThreeJS mesh sphere?

PS: I believe this is different than the lot/lan parameters which just specify the initial viewing direction but do not tilt the axis permanently, right?

Start by locating the ThreeJS mesh sphere creation and the existing EXIF or lot/lan orientation handling; the issue does not name specific files or tests. Review the linked Zenith data references, then verify that ZenithX, ZenithY, and Compass rotate the viewer without rewriting the JPEG and without replacing the initial viewing direction behavior.

Written by the indexing model from the issue text.