New hook, UserRequiresHTTPS

Intended for situations where current user can't technically access the
site over a secure connection, e.g. due to a terribly obsolete browser or
WP Zero carrier that provides only insecure free access to the site.

Change-Id: I343985092c49a21fa347ca4dc0e5ec27774ad11d
Merge "New hook, UserRequiresHTTPS"