Add FOSSology to ci-license-scan

To improve license scan process we add license scan using a `FOSSology`
server.

The `fossology.py` adds an `ApertisFossolgy` class which is able to:
- request upload of source code from Git server to FOSSology server,
- retrieve references of previous scan for this source code,
- request scan of the source code,
- download analysis report.
- remove FOSSology header, project's name in file path and sort files

This class is used in `ci-licence-scan` to generate the
`debian/apertis/copyright.fossology` file.

Signed-off-by: Frédéric Danis <frederic.danis@collabora.com>