Remove dbbackup integration

- Data dumping and restoring is now very complex!
- We should use the invoke export-records function now, rather than relying on dbbackup / dbrestore
- Documentation will be updated to match

docker/Dockerfile

@@ -21,7 +21,6 @@ ENV INVENTREE_MNG_DIR="${INVENTREE_SRC_DIR}/InvenTree"
 ENV INVENTREE_DATA_DIR="${INVENTREE_HOME}/data"
 ENV INVENTREE_STATIC_ROOT="${INVENTREE_HOME}/static"
 ENV INVENTREE_MEDIA_ROOT="${INVENTREE_DATA_DIR}/media"
-ENV INVENTREE_BACKUP_DIR="${INVENTREE_DATA_DIR}/backup"
 
 ENV INVENTREE_CONFIG_FILE="${INVENTREE_DATA_DIR}/config.yaml"
 ENV INVENTREE_SECRET_KEY_FILE="${INVENTREE_DATA_DIR}/secret_key.txt"