If an administrator has specified URLs to their privacy policy and/or

terms of service, and marked that they want users to consent to the use

of their data, they ought to get the user's acceptance of these

policies.
This involves several small, related parts:

Added a way for admins to link to their terms of service (which is

  almost always separate from the privacy policy).
Added the consent requirement for the policies. This is only added to

  the registry in the case where one or both of the privacy policy and

  terms of service URLs are set.
Added some logic to repopulate the registry of consent requirements

  when siteconfig changes.
Modified the valid_prefs_required decorator to not only ensure that

  users have made a choice about the policies, but that said choice is to

  accept them.

Tested the various visual states of the requirement in the privacy

  choices UI (privacy policy only, terms of service only, both), and in

  all states (no choice, accepted, rejected).
Tried to load my dashboard with no choice selected; was redirected to

  the settings.
Tried to load my dashboard with the policies rejected; was redirected

  to the settings.
Accepted the policies and was able to load the dashboard.
Ran unit tests.