Added an option for the default list icon, instead of being hard-coded
to 'arrow-r'

ul

This provides the ability for the follow cases:

1. set the option as default for all listviews using the $.mobile object
2. set (or override the default) icon with data-icon on a listview or with
the option icon if that listview is created programmatically
3. override the above for a list item with data-icon on that specific list
item

Moved listview icon option to the correct place alphabetically in docs.