Refactored application variables

roles/docker-postgres/tasks/main.yml

@@ -7,7 +7,7 @@
 - name: Install PostgreSQL
   docker_container:
     name: central-postgres
-    image: "postgres:{{postgres_database_version}}"
+    image: "postgres:{{applications.postgres.database_version}}"
     detach: yes
     env:
       POSTGRES_PASSWORD: "{{ central_postgres_password }}"