OmeroPy: src flake8 (I)

See https://trello.com/c/vnojR45Q/43-flake8-omeropy. This PR is the first of a series dedicated to have `components/tools/OmeroPy/src` compliant with the PEP-8 style.

To review this PR:

- check Travis is green, especially that `flake8 -v components/tools/OmeroPy/src`  validates the files modified by this PR
- check the integration tests are still passing

/cc @ximenesuk
That this can be omitted I find a bit surprising.
```
[hudson@ome-c6100-3 ~]$ cd OMERO-5.1-merge-integration/
[hudson@ome-c6100-3 OMERO-5.1-merge-integration]$ PYTHONPATH=lib/python/ python
Python 2.6.6 (r266:84292, Jan 22 2014, 09:42:36) 
[GCC 4.4.7 20120313 (Red Hat 4.4.7-4)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import omero.sys
>>> omero.sys.ParametersI()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'module' object has no attribute 'ParametersI'
>>> 

# Now manually add this line back to the file
[hudson@ome-c6100-3 OMERO-5.1-merge-integration]$ vi lib/python/omero/sys/__init__.py
[hudson@ome-c6100-3 OMERO-5.1-merge-integration]$ PYTHONPATH=lib/python/ python
Python 2.6.6 (r266:84292, Jan 22 2014, 09:42:36) 
[GCC 4.4.7 20120313 (Red Hat 4.4.7-4)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import omero.sys
>>> omero.sys.ParametersI()
object #0 (::omero::sys::Parameters)
{
    map = 
    {
    }
    theFilter = <nil>
    theOptions = <nil>
}
```