function getConfigFile () {
	// FIXME: This function should be in core. Do you want refactor me ;) ?, be good!
	return path.resolve(process.env.MM_CONFIG_FILE || `${rootPath}/config/config.js`);
}
Returns a string with path of configuration file.
Check if set by environment variable MM_CONFIG_FILE
@returns {string} path and filename of the config file