Integration library

See https://trello.com/c/8IkxJlSD/323-integration-library

The `library.py` file under `OmeroPy` is used for integration tests by many components including `OmeroFS` and `OmeroWeb`. To simplify upcoming work on this test library, it is now migrated under `components/tests` as a standalone package. The hardcoded `PYTHONPATH` patching in `OmeroWeb` is removed from `setup.py` and the library is added to the path in `test_setup.py`. Note this may have consequences on low-level `py.test` usage (where the integration library needs to be manually added to the `PYTHONPATH`).

--no-rebase