Allow moderation without cross-site tracking

This is somewhat similar to Comments moderation from Admin Dashboard but is different enough that I felt it deserved its own post.

Right now the only way to moderate comments is for Ghost to read your admin cookie. If using a custom domain that means cross-site cookie tracking needs to be turned on in order for Ghost to know that the logged in member is also the admin.

As a Wordpress user of 20 years, I’m familiar with an interface that lets the admin mark any member as a content moderator. This would avoid the need to read your admin cookie when logging in as a user because simply logging in as a user marked as a moderator would give you the necessary privileges.

As an added benefit, you could conceivably have multiple moderators for the same site, which would be helpful if someone leaves a comment while the other moderator is not available.