The customize routes add CSS classes that make these admin
config pages look different from the ones under /admin/config.
We want all config routes to be under /admin/config as well.
This commit moves the emoji, user fields, and permalinks pages
out of customize and into config, updating all references and
adding more rails routes as needed.
Also renames admin emojis route to emoji, emoji is singular and plural.
The Admin UI guidelines states that buttons should have text, not icons. This was an oversight on the admin emoji listing.
Part of this change is also opportunistically removing the CSS file for admin emojis, none of which is used any more since the conversion.
