fix authelia_db_postgres_password. Add main_species in "citrus_sinensis.yml". Fix authelia_secrets_env_path in traefik_compose.yml. Update Readme

Move constants to file constants.py. Change config root to dict and update parse_config(). Change some config parameters name (galaxy_persist_data, tripal_banner_path, jbrowse_menu_url), update example config file and compose templates. Remove apollo config variables (webapollo_user, webapollo_password) in config file and in gspecies compose template, because apollo service not deployed here. Factorize parse_input() et parse_config(). Update description of scripts in main. Set default config file in scripts. Remove useless variable datasets_to_get in gga_get_data.py. Update README.md.

Update compose files, authelia config. Fix banner. Write galaxy_nginx.conf only if needed. Modify authelia_config_path condition. Modify get config args. Remove deploy_stack_for_current_organism.instance_url

removed backup gspecies template file, precisions for required/optional parameters in config_example.yml