Add more firewalld service and fix typo in one
Add support for zones in firewall service
Setup network interfaces into external and internal zones

This replaces the /etc/init.d/(freedombox-)proxy script
that enables masquerading traffic from internal interface
using and external interface. It makes the same assumptions
about the nature of network interfaces as the proxy script.

FirewallD automatcially takes care of loading masquerading
modules, enabling kernel parameter for forwarding and
allowing masquerading using external interfaces.