New arguments for scripts/ngds_config_file.py

Added a 3rd arugment when running ngds_config_file.py so the directory location of ckanext-ngds can be passed in and the file references can be properly set up. However, ("ngds.bulk_upload_dir", "/home/ngds/work/bulkupload/") and ("extra_public_paths", "/home/ngds/extrapublic/") still need to be fixed manually.