XD-2069 Enable HTTP source debugging

- Add logging statements at DEBUG level in NettyHttpInboundChannelAdapter
- Add HTTP source module option for more verbose logging via Netty's own LoggingHandler, which can be turned on by `--verboseLogging=true` in the stream definition

@dturanski - I believe that we do, based on how this works.

The LoggingHandler must be added to the pipeline explicitly (see the adapter code) in order for Netty to actually log anything, which is what verboseLogging controls. The question is, at what level do we want that output? DEBUG seems more sensible to me.