v2.1 Major Update - Folder Migration

Integrated a subroutine on update, to add a custom property to the
Citable_Documents folder and rename it to Citable. We now query the
folder using the custom property, so the name can be anything. If the
occasional edge case where this fails, users need only move their files
to the new folder. This is more flexible than adding a custom property
to the individual files.

Also added numerous visual refinements including an svg image for the
select element, and thus updated the button styles. Still not super
happy. TODO: do a visual study to redefine the look. Also updated the
padding around the menu items to improve focus behavior and tweaked the
butter design. TODO: move to a sass system.