Allow instance admins to add custom CSS that will affect
every page of their instance.
This is done with a new CustomCSS instance setting that
works pretty much exactly like the Users CustomCSS property.
This custom CSS is then requested for every page load.
User styles/themes take precedence over this CSS.
* use apiutil + paging in admin processor+handlers
* we're making it happen
* fix little whoopsie
* styling for report list
* don't youuuu forget about meee don't don't don't don't
* last bits
* sanitize content before showing in report statuses
* update report docs
