XD-614 Channel Registry Conversion Improvements

Convey contentType and originalContentType in message to allow
proper decoding on the inbound side.

For Redis, add the headers to the payload of the transported
message.

XD-614 Polishing

PR Comments.
XD-622 Various Javadoc Fixes

Remove warnings from build.
XD-626 Shell: RestTemplate not posting using UTF-8

XD-626 Add Integration Tests

XD-626 Code review changes