Parts framework

The branch has been neutered to remove the parts frontend, leaving only the kits. The idea is to get the kit listings out (which work fine), and finish the rest of this framework in a new branch, "fix-parts-framework". 

Once this is pushed live, the kit listings will have to be added manually with the kit builder, which is also not fully completed, but will work in a pinch. 

We shouldn't merge this until immediately before we can add the kit listings, because the kits page will be blank until stuff is added.

Basically let's just get this mother into master and go from there.