Add a --chaoss flag to generate a report using CHAOSS only metrics (the current report)

[aswanipranjal]

Following #111 what we want is to add a --chaoss flag which will allow the user to generate a report using CHAOSS metrics only i.e the current report that is being generated.

This will be the default behaviour of Manuscripts and this will allow us to add different flags (--gmd, --risk and so on) which will be responsible for generating reports using different metrics.