Feature/homepages

First real implementation of a homepage template in the new home-templates system. This also includes a new "Series Posts" widget for highlighting a few posts from a series (for use on the homepage) as well the functionality for the "post types" vocabulary that includes the icon meta-field.

I'd love it if you could review this code to see that it makes sense to you before I take this homepage template (and all the stuff that had to come with it) and create several new variants of it for Wisconsin Watch... don't want to go too far down the homepage layout rabbit hole without knowing that it fits the bill.