Add log diagnostic context

Add log diagnostic context

As it's not trivial to use MDC directly from logging framework in
reactive application, we need to do some work manually. The approach
proposed is an explicit MDC handling, which means that context is
kept as an object created after establishing client connection. Next,
new instance of HvVesCollector (and its dependencies) is created. Every
object is propagated with ClientContext so it can use it when calling
logger methods.

In the future ClientContext might be used to support other use-cases,
ie. per-topic access control.

As a by-product I had to refactor our Logger wrapper, too. It already
had too many functions and after adding MDC number would be doubled.

Change-Id: I9c5d3f5e1d1be1db66d28d292eb0e1c38d8d0ffe
Issue-ID: DCAEGEN2-671
Signed-off-by: Piotr Jaszczyk <piotr.jaszczyk@nokia.com>