Improved request-response logging

[kdgrant]

I'm finding the request/response logging facility a bit clunky to use, since the request & response end up in different log files and need manual handling to correlate:

MONACO_REQUEST_LOG=./request-log.txt MONACO_RESPONSE_LOG=./response-log.txt ... 

When specifying the same file for both requests and responses (MONACO_REQUEST_LOG=./log.txt MONACO_RESPONSE_LOG=./log.txt) the output is arbitrarily interleaved and truncated, so this isn't a solution (it was worth a try!).

Suggestion
Support a MONACO_REQUEST_RESPONSE_LOG environment variable.

When this is present, requests and responses would be written to the named file as request-response pairs, ordered chronologically by request time.

[didiladi]

@kdgrant That's a good idea!