add_key() -> add_verification_key()
remove_key() -> remove_verification_key()
release.json -> snapshot.json
Update repository_tool-diagram.png
Update README following the renamed functions and release role changes.
Minor edits, such as removing lint left over from a previous merge conflict.
Allow leading os.sep for target and restricted paths listed in metadata. Previously, '{repository directory}/targets/file.txt' was listed as 'file.txt' and unsuccessfully compared against '/', or the root-most targets directory. Now, '/file.txt' & '/' and similar examples may be compared and verified.
Fix issue where a hashed bin with empty targets was flagged as invalid because its targets did not produce a path hash prefix that matched any of those listed in the parent role. Uncovered with _ensure_all_targets_allowed().
Minor edits to code that compared paths and and used path separators.
