config lib updates
- ability to get config values from a .json file with the
\flat\core\config::get_ref()
method - a config value in a .php config file (which are obtained with the
\flat\core\config::get()
method) can refer to a config value from a .json file by making it's value in the .php config file a string with the following format:CONFIG-REF::json_file_basename.property_name