Via header for response and request is fully stabilized and present according
to the RFC now.

Important information, like protocol and protocol version are exposed.

Hops which were present in the request are stored and descriptively named.

Versions of components are exposed in hidden way and in the same time the
frontend administrator and frontend user are able to analyze the versions,
and the version history present on the node is transmitted back.

Additionally each node can be identified by frontend admins and users for
request and response headers, allowing more debugging.

Improve the tests by extending assertSlaveBase and reuse it instead of
duplicating the code everywhere.