SMS: Add a switch to use_kannel (or not)

If we don't use kannel, then create the runit link in /etc/service
to run the python esme.

modules/rhizo_base/templates/config_values.py.erb

@@ -56,6 +56,7 @@ kannel_server = '<%= @kannel_server %>'
 kannel_port = <%= @kannel_port %>
 kannel_username = '<%= @kannel_username %>'
 kannel_password = '<%= @kannel_sendsms_password %>'
+use_kannel = '<%= @use_kannel %>'
 
 # VOIP provider
 voip_provider_name = "<%= @voip_provider_name %>"