add dummy env vars to the Dockerfile (#67)
add dummy env vars to the Dockerfile (#67)

* add dummy env vars to the Dockerfile

Without values for some env vars, it is not possible to build a
docker image for the application. Having dummy values means an
image can be built, with real values supplied at deployment time.

* Add DATABASE_URL, for consistency

ministryofjustice/tax-tribunals-datacapture,ministryofjustice/tax-tribunals-datacapture,ministryofjustice/tax-tribunals-datacapture,ministryofjustice/tax-tribunals-datacapture