Add IPD slider and lock the camera settings in Omni-Directional Stereo mode

Omni-Directional Stereo has a few issues:

* **No IPD Slider** - Different headsets have different IPD so it would be nice to render at different IPD without having to build Chunky.
* **No Aspect Ratio Lockout & FOV Slider Broken** - Changing aspect ratio breaks the FOV and therefore breaks the image in a 360 viewer, as for locking out the FOV, it's tied to the aspect ratio and the slider becomes useless so hiding it might be for the best unless you want to fix the FOV slider to change the AR to allow for 180 or 360 degree stereoscopic images.
* ~~**Extreme Image Distortion** - I'm not sure if the wavy block distortion at the top & bottom of the image is from the [Image Viewer](https://maddog443.github.io/rs-sphere-test/) or from Chunky.~~

Start by locating the Java code for Omni-Directional Stereo camera settings and the aspect-ratio and FOV controls. Reproduce the current behavior, then define completion as an adjustable IPD and camera settings that preserve valid 180- or 360-degree stereoscopic output; the withdrawn distortion concern is not part of the requested work.

Written by the indexing model from the issue text.