Extract firewall definitions to their own recipe

This allows us to use them for KVM hosts as well. Until now we had set
up ufw rules manually on the two KVM hosts (draco and centaurus)

Refs #244

site-cookbooks/kosmos-bitcoin/recipes/source.rb

@@ -158,9 +158,4 @@ systemd_unit 'bitcoind.service' do
   action [:create, :enable, :start]
 end
 
-# TODO move to custom kosmos cookbook before publishing bitcoin cookbook
-firewall_rule 'bitcoind' do
-  port     [8333] # TODO adjust for testnet
-  protocol :tcp
-  command  :allow
-end
+include_recipe "kosmos-bitcoin::firewall"