Use FORCE_SCRIPT_NAME and STATIC_URL in `web iis`

Example:
```
C:\tmp>OMERO.server\bin\omero config set omero.web.force_script_name /test-omero

C:\tmp>OMERO.server\bin\omero config set omero.web.static_url /test-static/

C:\tmp>OMERO.server\bin\omero web iis

0 static files copied, 816 unmodified.
Configured Virtual Directory: /test-omero
Configured Virtual Directory: /test-static
Installation complete.
```

OMERO.web should be running under http://localhost/test-omero/
Note only top-level prefixes work.