Flake8 Bio-Formats Python files

While assessing the amount of `flake8` errors for the openmicroscopy repository, many warning arise from the presence the Bio-Formats submodule. This PR cleans up the Python files of the Bio-Formats repository, mostly under `xsd-fu`. A couple of external files are excluded from the top-level `flake8` via a `setup.cfg` file.

Is it worth adding the `flake8` check to the Travis build? If so, which component?