modify property name for submissions.interface

In ECMAScript 3, objects are not allowed to have unquoted properties
with the same name as a reserved word (ex: 'interface'). Since there's
no reason to break compatibility for something like this, we'll just
rename the property.
remove structure to apply bookends to selections

The initial implementation was applying a CSS class that would hide the
bookends. This interface works fine without modifying the DOM to
indicate the range is 'special' with persistent indicators.