Sphinx api improvements

Following @rleigh-dundee's effort to convert the aut-generated Python API to use Sphinx, this PR makes cosmetic adjustements to the generated API for proper inclusion/announcement with the 5.0.3 release:
- pass the release number to the documentation (same as javadoc and slice2html)
- re-import the configuration from ome-documentation and simplify `conf.py`
- redirect the main overview page to point at `python` rather than `epydocs`
- use OMERO.py rather than OmeroPy
- include the OME logo (svg version - to be tested udner various browsers)

The output of this PR should be published and reviewable under http://ci.openmicroscopy.org/job/OMERO-5.0-merge-build/ICE=3.5,label=ome-c6100-1/javadoc/python/ (or whatever Ice version you choose).

Items not included in this PR but will be part of future work:
- drop `epydocs` completely. As @rleigh-dundee suggested, we can either do that on 5.1.x solely and preserve it on the 5.0.x line or in-between 5.0.3 and 5.0.4
- redirect all the documentation Python api linksto `python`: this requires the Sphinx-generated API to be published. This is very likely a post-5.0.3 release item /cc @hflynn
- fix the docstrings: as discussed previously this is a larger body of work involving rebase issues and should be tackled independently (summer project?)
What's the reason for this change?  The property name also needs changing if this is needed or else it's a bit confusing!