Implement "Recent Actions" box on the admin2 index page

[audreyfeldroy]

To start, admin2 needs to display something like this when no actions have been taken:

There should be a Recent Actions box on the right side.

Right now we just have a TODO:

Then, at least add/edit/delete actions for all users should be tracked and shown in admin2, like this:

Side notes:

• @pydanny says that the original django.contrib.admin implementation of Recent Actions was a bit difficult to work with. He has some ideas about how to improve it. Talk to him if you decide to attempt this issue.
• Also see issue Implement app-level "Recent Actions" #200 about displaying Recent Actions at the app level. Consider this in your implementation.