Move the dashboard product list to django-tables2

Before you merge this I'd port over the other tables as well. This is primarily for review. A few things:

* Getting the sorting icon into the header is a little bit hacky, with an `<i class="icon-">` to trigger the necessary CSS rules for FontAwesome. Also the unicode character value for the chevrons up and down had to be copied. If FontAwesome had less mixins we could use that.
* Sorting and tab are kept when the title link is used (this was a bug in the original product list)
* You can sort by UPC, Product class, status or parent as well

Other than that I'm impressed with the `django-tables2` source code. The repository doesn't look very active, but the code is very high quality from what I've seen today.

Let's see what travis says :)