tools: Add reading KNOT Register response
tools: Add reading KNOT Register response

This patch extends ktool to display the received credential as result
of the KNOT registration procedure.

CESARBR/knot-service-source,CESARBR/knot-service-source,CESARBR/knot-service-source,CESARBR/knot-service-source,CESARBR/knot-service-source