Tabs Test: AJAX Source as String

This test demonstrates loading content from an external source by adding a "source" setting defined as a string, which will be translated to a URL. Each tab's "href" will be passed as a parameter to the URL when the tab is activated. No tab panels exist in the base markup, but the markup is generated the first time each tab is activated. On subsequent activations, the existing tab markup is used instead of making a new AJAX call.