Add --update option to deploy create

To allow updating an existing deployment

- Check the deployment dir exists when updating
- Write to temp dir, then safely copy tree
- Don't overwrite data dir or config.env

stack_orchestrator/data/compose/docker-compose-test.yml

@@ -8,6 +8,8 @@ services:
       CERC_TEST_PARAM_2: "CERC_TEST_PARAM_2_VALUE"
       CERC_TEST_PARAM_3: ${CERC_TEST_PARAM_3:-FAILED}
     volumes:
+      - ../config/test/script.sh:/opt/run.sh
+      - ../config/test/settings.env:/opt/settings.env
       - test-data-bind:/data
       - test-data-auto:/data2
       - test-config:/config:ro