Permalink style

This pull implements a second UI mode that places the ShortURL input controller below a page's permalink input and styles it in a similar way:

 - Added a setting (and screenshots) to select the UI mode
 - Refactored (consolidated) input rendering code into two functions that respond based on UI mode
 - Added a function to render input for 'edit_form_after_title' region
 - Added logic to dynamically select add_action and wp_enqueue_style based on UI mode

The mode could use some further enhancement, but I wanted my first pull request to minimize the impact of my changes on existing code.