Flake8 omero/util

This PR fixes the flake8 warnings from `omero/util`

One external file has been moved untouched to `omero_ext`. Three files have been removed, these are all: unimported by anything and: have no main method, are clearly old or are clearly broken.

Travis and Jenkins should both pass.


It's been that way since the beginning: 3916fd5e94dca839aff5140b7b5c5507898cc745

The only side-effect I can think of is that it would throw if `obj` is not a proxy. I can't think of anything that's relying on that behavior and the later methods would *also* throw, but probably harmless to leave as it is (though possibly slightly confusing).