Revised Dashboard

### The problems

I spent a bit of time looking at how we organize our content pages in Concerto 2. We had a bit of an identity crisis going on with the browse page, admin "dashboard," and other admin pages. Furthermore, there wasn't enough useful stuff on the current browse page to call it a dashboard - it wasn't providing a heads-up to anything besides content and a few user-centric details. Finally, we had both the Concerto logo button and the "Browse" / "Dashboard" buttons in the top menu directing to the same page.

In assessing the information architecture I came to the conclusion that a dashboard still made sense but needed some extra functionality in order to serve as a home base or table of contents for the other pages of the application. I was inspired by the dashboards of other admin panels, such as that of Wordpress. 

### The proposed solution

The revised dashboard acts as a summary of the key bits of information from the various sections of the application. It is only accessible when a user has logged in - otherwise, it will redirect to the standard browse content page. When logged in, the dashboard shows sections relative to the abilities provided to the current user: admins will see the admin stats partial that was previously on the admin preferences page, and users will see their groups and screens. The activity log has a more prominent look, and there's a space for the network vitals (which have been fleshed out from earlier). This dashboard is now linked through the big Concerto logo button, while there's a menu item under "Content" dedicated exclusively to the browse listing.

The other part of this is that I clarified the admin pages: what was previously called the "admin dashboard" is the Global Settings page. The Plugins page has been extracted to its own view with menu item. Assuming this pull request goes through, @augustf is planning to rename the dashboard_controller to concerto_settings_controller to make the code consistent with the interface.

### Check it out

I have attached a screenshot of the new dashboard page. Please try it out when you get a chance. Does this all make sense?

![screen shot 2013-06-13 at 10 19 34 pm](https://f.cloud.github.com/assets/157865/657757/e99ad866-d582-11e2-9919-6fd0599be208.png)