Tracing: A bunch of tweaks to trace output and use.

* Adds pipeline ids in a few places.
* Uses JSON.stringify to output text values to prevent "\n" from
  breaking trace output lines.
* Some minor formatting tweaks to tracer to prettify it a bit more.
* Split long env.log lines to be under 100 chars wide.

Change-Id: I14f245e64e127e4e9c922879be860dbbd74ed6fb