Don't embed config options directly in Javascript. Including them in the
Javascript forces us to recompile the Javascript whenever these options
change, which requires us to redeploy the entire site instead of just
restarting the app server.
Try to prevent malicious sites like danbooru.me or idanbooru.com from
proxying our site and inserting ads. If we detect that we're not running
on the real site, then we redirect to the real site.
* Add Discord, Twitter, and Github links to site footer.
* Remove "Desktop mode" and "Keyboard shortcuts" links from footer.
Users can use the desktop site option in their browser to switch
between desktop and mobile mode.
* Remove git hash from footer. Users can hover over the Github logo to
see the hash instead.
Refactor things to store information about the current user as data
attributes on the <body> tag rather than as <meta> tags. These <meta>
tags are now deprecated and will be eventually removed.
* Store all of the current user's API attributes as data attributes on
the <body> tag.
* Add `CurrentUser.data` for getting data from the <body> tag, and
use it instead of `Utility.meta`.
* Add `CurrentUser.update` for updating the current user's settings.
* Fix a bug with the user named "Anonymous" not being able to edit notes.
