Improved documentation for ListView

[Isaac-Leonard]

I'm attempting to build a table component, similar to what's in the todo list example but can't seem to get anything to display and the most progress I've been able to make is to have the item_for method being called with an index that's double the number of rows. Would it be possible to improve the module level documentation for ListViews to explain how they are meant to be used and to add more detailed comments to the todo list example please. For context I've not done any object c stuff before so am not aware of how the original framework really works.