Adding a python script to enable updating new goldens into
a staging branch in the golden repo (filament-assets).
The same script can be used in github workflow to automatically
create a golden staging branch. This will be useful for users
without access to a mac (the only platform for generating
goldens as of now).
PPM does not store alpha channel, but TIFF does. We add a method
to export RGBA to a TIFF file without compression.
We add the corresponding options to gltf_viewer and
AutomationEngine.
The default export format for both gltf_viewer and AutomationEngine
is now TIFF.
