python: Use os.path.isdir(p) rather than p.isdir()

The latter is broken with Python 2.7 on Windows.
OmeroPy: Document path.py changes
OmeroPy: config.py works with Python 2.7 on Windows
OmeroPy: Update methods in path.py to wrap os.path properly

Merge the changes from
https://github.com/jaraco/path.py/commit/bee13d0de4d44599d397b603e1c83dce1ce9818d
Revert "python: Use os.path.isdir(p) rather than p.isdir()"

This reverts commit 2ee95fa1d3f800c3ad16069c051c12b9a750b8e1.
Merge pull request #2386 from rleigh-dundee/python-isdir-dev50

OmeroPy: Fix path handling and renaming for Python 2.7 on Windows