Add a way to run tests in PostgreSQL in Docker (#3699)

test_postgresql.sh

@@ -0,0 +1,12 @@
+#!/bin/bash
+
+# This script builds the Docker image to run the PostgreSQL tests, and then runs
+# the tests.
+
+set -e
+
+# Build, and tag
+docker build docker/ -f docker/Dockerfile-pgtests -t synapsepgtests
+
+# Run, mounting the current directory into /src
+docker run --rm -it -v $(pwd)\:/src synapsepgtests