Add request/response to subunit-describe-calls

Adds new functionality to subunit-describe-calls. Request & Response
headers + body information now included in JSON output. Makes
-o/--output-file parameter optional, if not specified a shortened output
will be created. Changes the -s/--subunit parameter to not allow for data
to be passed in via stdin.

Change-Id: I44c6b7f9adef7e5be2039c7201f17485f2a46077
3 files changed