Add a way to append the config-store from mdml-tools to a custom project

At the moment I am importing the data-classes in my own project and then add them to my own configstore objects as nodes. It would be even better if the mdm_tools had a function like add_mdml_to_config_store or similar, so that with one line I can import the complete mdml_tools structured config objects at once. They would only have to be defined once in the add_mdml_to_config_store function.