refactor logging

Logging right now is a bit of a hodgepodge.

Fundamentally, the right things are being logged so this is relatively low priority, but some ideas:

1) Can _all_ logging output have a per-request uuid attached to it? Is this a more meaningful logger namespace?
2) Should logging use bunyan?
3) Should logging output newline-separated json?

The issue names no files, tests, or logging entry points, so first trace how logging is configured and emitted across the service. Compare the three proposed directions—per-request UUIDs, bunyan, and newline-separated JSON—and define a focused scope and verification plan before changing anything.

Written by the indexing model from the issue text.