This builds a python module granting access to the cddl-cat crate.

To "install", copy target/release/libcddlcat.so to some place in your python sys.path, and rename it to cddlcat.so.

TODO list:

• Add help to python objects
• Make ValidateError visible so that "except ValidateError" will work.
• Grant access to more cddl-cat functionality:
  • flatten_from_str
  • BasicContext::new
  • Context.rules.get(rule_name)