remove old, unused images

The `cap` images were used to create rounded borders around boxes, the `ui-` images were used with jQuery UI. None of these are used in the current design iteration.
Merge pull request #234 from pophealth/remove_old_images

remove old, unused images
Added comparator to sort in a more intuitive manner.
Parse the rootProvider to ensure when it is created.
Added or to return either the parsed int or the extension to default to a string sort.
Removed sortable_extension since it is no longer being used.