* Add new sample app: image_viewer
This app shows how to load and visualize images. It's also useful to work
on color grading and other post-processing effects by just loading an HDR
or EXR image as a reference.
This change also adds a new exposure setting to the color grading LUT.
* Fix comments and build
* Fix Metal
* Use high precision for the UV coordinates
* Fix refactoring issue
127dd8f675