omego install and upgrade Windows

Pip install omego, create an empty DB and repository. Then:

1. Create an empty config file (note the ability to use a custom config.xml has been in omego for ages, we've just never used it and it could do with some additional work to prevent it unintentionally using the wrong config file).
2. Install the latest release
3. Upgrade to 5.1 breaking
```
echo ^<icegrid^>^</icegrid^> > config-empty.xml
c:\Python27\Scripts\omego install -v --dbhost localhost --dbname omero --initdb http://downloads.openmicroscopy.org/omero/5.0.5/artifacts/OMERO.server-5.0.5-ice35-b47.zip --cfg config-empty.xml
c:\Python27\Scripts\omego upgrade -v --branch OMERO-5.1-breaking-build --dbhost localhost --dbname omero --upgradedb
```
Unix platforms should be unaffected.