Log a request unique identifier based on HTTP header

We want to log a **request unique identifier** coming from a HTTP request. This id is added by Apache Front just before calling a Knot.x instance. So we want to read this data from the request and put this data into log file (retrieving this value from _HTTP header_). Usually this is achieved by **MDC** in Slf4j but in vert.x application it is not good approach. More details here:

https://groups.google.com/forum/#!topic/vertx/SKrG5EWw090

Please find a solution for this problem.

Start by reviewing how the Vert.x application receives the HTTP request and writes its log file, with the Apache Front header and SLF4J/MDC discussion as context. Done means the request identifier from that header is available in the relevant log output without relying on MDC.

Written by the indexing model from the issue text.