* each log line is a json object
* structured logging allows logs to be ingested by machines and the logs to be indexed and queried addresses #1105
* structured logging allows arbitrary properties to be appended to each log line, and ingestion of logs to remain robust
* Structured logging provided by `pino` library
* Add `express-pino-logger` dependency
* Remove `debug`, `morgan`, and `morgan-debug` and replace with structured logging
* `console.log` & `console.error` replaced with structured logging in backend
* Remove `DEBUG` environment variable and replace with `LOG_LEVEL`
- Note that there is a test which reads from a logged line on `stdout`. This is not robust, it would be better to use the childProcess.pid to look up the port number.
* Log errors at points we explicitly send error to Sentry
* Amend indentation of a couple of log messages to align indentation with others
Iain Sproat