PR: Support Functions-php

[dmitry-kurmanov]

https://github.com/surveyjs/surveyjs-wordpress/issues/51

/**
 * Custom Save Survey Result function
 * file functions.php
 */
function surveyjs_save_result($SurveyId=null, $Json=null, $TableName=null) {
    /*do stuff*/ 
}
add_action( 'wp_surveyjs_save_result', 'surveyjs_save_result', 10, 3 );