SLING-2989 - [Tooling] integrate with vlt once available

Make the TracingCommand part of the api bundle to allow other transport
implementations to reuse it.

git-svn-id: https://svn.apache.org/repos/asf/sling/branches/tooling-ide-vlt@1514759 13f79535-47bb-0310-9956-ffa450edef68