Plugins + Scripts PictureToSkybox

1. Optimization: a problem that may not work when adjusting "specIntensityMul".
2. "3D Layout" and "Type" are only displayed in VR mode to avoid misleading. These two options are only effective in VR mode.
3. When in 3d layout, fix the correctness of environmental reflection.
4. Provide 3d layout a sample picture（capture from The Witcher 3）.

This update adds a core function: the skybox generated by the picture supports the native environmental reflection.
The following is a demonstration video.

1. Add support for hemispheres. In this way, you can reduce the package size by half without reducing the quality of the sky ball.

2. Additional parameters have been added.