rebased OmeroPy/src/path.py onto upstream version 5.2
path.py: walk: "errors" now defaults to "ignore", consistently with os.walk
path.py: listdir: added "unreadable_as_empty" kwarg
updated lib/licenses
added test module for custom modifications to path.py
Merge pull request #2835 from simleo/update_path

Update OmeroPy/src/path.py