Feature/default nym api (#2898)

* Setting default 'id' if not provided

* Modified 'NymConfig' to always require 'id'

* moved creation of nym-api directories away from 'override_config'

* missing optional id usage in nym-connect

* changelog

* Removed default value for '--id' argument

mixnode/src/node/mod.rs

@@ -58,7 +58,7 @@ impl MixNode {
     }
 
     fn load_node_description(config: &Config) -> NodeDescription {
-        NodeDescription::load_from_file(Config::default_config_directory(Some(&config.get_id())))
+        NodeDescription::load_from_file(Config::default_config_directory(&config.get_id()))
             .unwrap_or_default()
     }