Fix selection bug and use rotation, not camera

DONE:
- Rotate sphere instead of using camera.lookAt(), like in Elphel
  webgl_panorama_editor
- Allow to set initial heading / tilt / roll via "rotation" object
- Fix selection bug affecting rotation with mouse

TODO:
- convert to and from lon/lat public values
- restore worldToTextureCoords() & textureToWorldCoords() functionality