New Google-Drive-like tabular display mode for home page

A couple of customers have requested a less Fischer-Pricey homepage layout, which shows vital statistics about each dataset in a tabular format. In particular, datasets with an error status should be far more eye-catching than their neighbours, and the date on which a dataset last ran should be clearer.

Here it is:

![screen shot 2013-12-03 at 14 48 20](https://f.cloud.github.com/assets/739624/1664634/3fb58286-5c2a-11e3-8df8-d5d475147b7f.png)

Users can switch between this "list" layout and the traditional "tile" layout using the buttons next to the search box. The preference is saved in their (`user.effective`) profile, so the display will remain the same when they (or anyone else) next logs into their data hub.