Admin Dashboard should provide meaningful at-a-glance information about civic-server

[bainscou]

I think a queue of evidence items that need admin review, is the most important to have on the dashboard.

Also, it might be nice to have an easy way identify conversations that might need moderation, like a particularly active comment page, or a record that has received an above average amount of changes.

[acoffman]

The Admin dashboard will now show:

• A feed of recent events on the site (new comments, suggested changes and evidence item submissions)
• A queue of evidence items that need attention (have failed processing or are awaiting approval)
• A feed of new user signups

We can obviously add whatever else becomes useful as we continue to dogfood the site!