Make the remote address rules for Settings > Activity Logs more consistent

Summary:
Depends on D18971. Ref T13049. The rule is currently "you can see IP addresses for actions which affect your account".

There's some legitimate motivation for this, since it's good if you can see that someone you don't recognize has been trying to log into your account.

However, this includes cases where an administrator disables/enables your account, or promotes/demotes you to administrator. In these cases, their IP is shown!

Make the rule:

• Administrators can see it (consistent with everything else).
• You can see your own actions.
• You can see actions which affected you that have no actor (these are things like login attempts).
• You can't see other stuff: usually, administrators changing your account settings.

Test Plan: Viewed activity log as a non-admin, no longer saw administrator's IP address disclosed in "Demote from Admin" log.

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13049

Differential Revision: https://secure.phabricator.com/D18972