REFACTOR: Remove $.cookie in favor of a local library based on it (#10548)

This helps us out in a few ways:

1. It lessens our reliance on jQuery
2. It's slightly less code because it omits options we don't use
3. It is one less library to import and put into ES6 modules

app/assets/javascripts/vendor.js

@@ -13,7 +13,6 @@
 //= require favcount.js
 //= require jquery.ba-resize.js
 //= require jquery.color.js
-//= require jquery.cookie.js
 //= require jquery.fileupload.js
 //= require jquery.iframe-transport.js
 //= require jquery.tagsinput.js