Initial commit: EDGE Ignition gateway docker-compose build

Custom Dockerfile-based build for an Ignition Edge gateway with
pre-baked base gwbk, module registration, and admin password
provisioning, backed by MariaDB.

gw-build/docker-entrypoint-shim.sh

@@ -0,0 +1,5 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# Kick off the built-in entrypoint, with an in-built restore (-r <gwbk path>) directive
+exec docker-entrypoint.sh -r base.gwbk "$@"