[Infrastructure] [Firewall] Initial UFW provisioning

:construction_worker: Throwing this out there for #307. This is a work in progress and needs further refinement.

* [X] iptables rules for web servers
* [x] iptables rules for Jenkins
* [x] Disable all access on IPv6

There are some major issues I see with getting this locked in the way we want:

* Provisioning happens in 3 segments, we can't use that information to apply rules related to Jenkins (allow SSH to the web server from the Jenkins box)

Whoops. Should have known that from having visited it. I'll make it 80 for now.

As for a var, the most top level we can set this at is within the "Configure web server(s)" section in each of `prod_web.yml` and `staging_web.yml`.