Convert all admin listings to views

[jenlampton]

This is an issue that will allow us to track the progress of...
Put admin_views in core

Administrative pages:

• Replace admin/people with a View in user module
• Convert admin/content to a View in node module
• Convert admin/content/comments to a View

[klonos]

What was wrong with the meta-issue? Can't we use that one instead of opening a new issue here?

[klonos]

@jenlampton: Do you still feel that we need a separate issue for this task? Or is it simply in order to have a milestone set for it (the parent meta-issue has no milestone set yet)?

[quicksketch]

I think we should just use the existing meta at #151 as well. Let's close this and consolidate over there.