The related object selector had an issue where some selected options were wrapping is very ugly ways. The implementation of this isn't particularly pretty or flexible, and we really need to just rebuild it all on top of a modern system, but for now, this change is going to allow us to improve the situation. This adds a couple static items to the selector class, `optionTagName` and `autoAddClose`. This allows subclasses to change the type of tag which is used for the individual selected items, and to control whether we append the close/remove action. With these, a subclass can choose other layouts for the selected items, such as a `<table>`. Some basic styles for using tables are included now as well. Testing Done: Updated the user selector subclass in Review Board to use a table instead of a list, and saw that lists of selected users that included very long usernames or real names no longer wrapped in terrible ways.