Add options to disable comments, the forum, and autocomplete. This is
for personal boorus and potentially for safe mode. Note that disabling
the forum may cause difficulties with creating and approving BURs.
Disabling comments and the forum merely hides them from most areas,
rather than completely removing them.
Disable the ability to upgrade to Platinum. The Platinum level still
exists, but users can no longer upgrade to it. Sales of Platinum are
being disabled in preparation of increasing the tag limit for Gold
users.
Factor out FontAwesome icons into a set of helpers. This is so that it's
easier to keep track of which icons we're using and easier to change
icons globally.
