Enable Sieve and ManageSieve for Dovecot

Enables both sieve and managesieved, and adds a global rule that moves
detected spam to a user's Junk folder automatically

site-cookbooks/kosmos_email/recipes/firewall.rb

@@ -32,3 +32,9 @@ firewall_rule "IMAPS" do
   port     993
   protocol :tcp
 end
+
+firewall_rule "ManageSieve" do
+  command  :allow
+  port     4190
+  protocol :tcp
+end