render: Change how we store render passes info. Previously we used a dictionary with integers as keys, which doesn't go well with JSON serialization. Now replace with an array of fixed length with items that are `None` by default.

--exclude=build
--exclude=dist
--exclude=docs/_cache
--exclude=docs/_counter
--exclude=bower_components
--exclude=node_modules
--exclude=docs/raw
--exclude=*.egg-info
--exclude=__pycache__
--exclude=__tmpfs__