Added url_helper samples

Created a demo explaining why I made a change to url_helper.php.

Also made the sample.php controller more dynamic by creating a generic
"view" function, which takes a parameter of the page you are requesting.
That way I don't have to create a function for every page I create.
Made a change to the url_helper

Made a change to my explanation.  If the second parameter is blank, I am
now replacing the $site_url text with a non-breaking space.