Allow progressive refresh instead of full refresh

There should be enough DOM information available to the auto-refresh frontend code, to allow it to correctly place the updated items in the existing View DOM.

Early version implemented in the latest dev.

More robust version now in dev. Here's how it works:

The basic idea is to provide an "update" view that will only return items that were added since the last refresh. This secondary view accepts a timestamp that is the time of the last refresh.

* Create original view. It has to support AJAX. Add the following PHP code to the header:

print theme('views_autorefresh', 5000, views_get_current_view(), array(
  'view_base_path' => 'liveblog/autorefresh', // the path of the update view
  'view_display_id' => 'page_2', // the display of the update view
  'view_name' => 'liveblog', // the name of the update view
  'sourceSelector' => '.view-content', // selector for items container in update view
  'targetSelector' => '.view-content', // selector for items container in on-page view
  'firstClass' => 'first', // class name for first element (optional),
  'lastClass' => 'last', // class name for last element (optional),
  'oddClass' => 'odd', // class name for odd elements (optional)
  'evenClass' => 'even', // class name for even elements (optional)
));

The header should show even if the view is empty.

* Create the update view. Typically, this would be a copy of the original view, with the path given above. The main difference is the addition of one argument, typically Node: Post date (with operator) that is also supplied by this module.

That's it!

Future features include:
* New items are only added to the top of the view. Eventually, there should be an option to add them to the bottom instead.
* Twitter style: display a message that informs the user there are more items, without displaying them until the user clicks it.
* Update page title with number of new items.
* Highlight new items for a given time.
* Package the functionality as a header plugin (or display add-on) for Views 3, and as a new display plugin in Views 2.
* Support multiple auto-refresh views per page.

Yes, it works the same.