After this commit, every non-key field is treated as if it was optional
while every key field (plus every auto-generated `Kind` field) - as if
it was required.
Here we start restructuring the the schemas YAML such that it
contains a top-level `version` field. In this commit we only modify
the YAML, the build system changes will come later, to avoid
enormous commits.
These schema files are currently generated at build time by
collecting various TUPLE-TREE-YAML comments using the
`extract_yaml.py` script. In this commit we move them to the codebase
but we don't use them yet, this will be done at a later commit for
the sake of readability.
Add the PipelineDescription object that describes the structure of a
pipeline. This will be used by all the downstream users instead of
pipeline accessor methods via PipelineC.
Ivan Krysak