Write docs about how to control reports

[craigfowler]

This should introduce the user to the various interfaces and extension points which relate to reporting.

It's touched-upon in this old Wiki content but not included in the main docs site:
https://github.com/csf-dev/CSF.Screenplay/wiki/GettingReports

[craigfowler]

Once all of #298, #299 and #300 are complete, the old Wiki may be unpublished.