`discourse-common` was created in the past to share logic between the
'wizard' app and the main 'discourse' app. Since then, the wizard has
been consolidated into the main app, so the separation of
`discourse-common` is no longer useful.
This commit moves `discourse-common/(lib|utils)/*` into
`discourse/lib/*`, adds shims for the imports, and updates existing
uses in core.
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.
