2. Now renderItemHTML wraps th1. Now expires==null, not undefined, if there is no expiration date.
e div in a <li> with data-pk=<item_id> so the sorting is easier.
3. Helper function uiGetItems() returns jQuery object with the items to be sorted.
4. uiSortByTitle, uiSortByPriority, uiSortByDate are now using the data in _items for sorting, not the data in the DOM elements.
5. Added sortBy() that creates a custom comparator function for tsort (TinySort) to accomplish sorting by any field, with the option of putting all null values last.
Now not wrapping <div>s with the items in <li>, because it is done automatically by renderAllItems().