Amazingly, the size field in PixelBufferDescriptor was often totally
incorrect for Java-based clients. The reason we did not notice: OpenGL
often consumes a pointer to image data without consuming a byte count
(e.g. glTexImage2D).
OpenGL infers size from dimensions + format, but Vulkan does not. This
caused texture corruption with Vulkan on Android.
This fix follows a pattern used in other places such as
FRenderer::readPixels.
* WIP Add helper to upload Android bitmaps to textures
* Add missing file
* Pass custom constants for bitmap formats
* Add sample app for texturing
* Update the README for samples
* Rename variable from callback to autoBitmap
This change will allow the skybox use a compressed texture format.
For now, the old internal format "RGBM" is still honored, but in a
forthcoming change we will replace the enum with UNUSED.
