Activity stream dashboard

[jace]

The admin dashboard currently features two graphs showing site activity. It should also include an activity stream showing each individual event as a separate textual item, with a link pointing back to the main URL.

As with #419, this activity stream should be a materialized view that is refreshed when an event happens.

Events to show:

1. New user registration
2. Draft job post created
3. Job post confirmed
4. Job post reviewed (moderated, rejected, etc)
5. Job application submitted
6. Employer response to job application (accepted, rejected, etc)

[jace]

This events should be viewable as a consolidated activity stream, or by type of event. Here is the dashboard UI from Eventframe showing this. Selecting any item from the list will only show objects of that type: