auto-fill the .txt and .yaml files in the plugin tree during install_plugin.py script #4

Rather than requiring plugin writers to manually list the import-style path to files containing e.g. recipe modules or LMVis plugins, etc., would probably be OK if we assumed any file in e.g. recipe_modules directory should have an entry in the config tree and take care of that for everyone during the config-tree copy in install_plugin.py.