Don't restrict the `bodies` folder to contain request bodies only
RawFileBody & ELFileBody can now be used for checks
Suffix bodies filename with type rather than request id

That allows for better grouping of bodies for a certain request, in
file listing or shell completion.
New recorder flag allowing to dump response bodies and add raw checks
Support base64-encoded content text (HAR 1.2)
Merge pull request #2073 from teads/response-checks

HTTP: Response checks, close #2072