Simplify dockerfile / docker-compose

- Single data volume now also includes 'static' files
- InvenTree source repo is now cloned into /home/inventree (to match the "dev" image)

docker/start_prod_worker.sh

@@ -0,0 +1,14 @@
+#!/bin/sh
+
+echo "Starting InvenTree worker..."
+
+sleep 5
+
+# Wait for the database to be ready
+cd $INVENTREE_MNG_DIR
+python manage.py wait_for_db
+
+sleep 10
+
+# Now we can launch the background worker process
+python manage.py qcluster