Home page Control Panel tour for "Administrator" users #4286

#4286

#### Changes

* Adds a "Take a tour" link to the /home page (works with or without "home" in the URL).
* Highlights each CP menu item, and the Section Settings gear
* Only appears for site members with permission to "access control panel"

![screen shot 2013-12-09 at 3 08 26 pm](https://f.cloud.github.com/assets/228733/1708400/b1605cac-610d-11e3-8ef2-24259cdabb38.png)