dch-gw: Initial commit

The *dch-gw* role, and the corresponding `dch-gw.yml` playbook, apply
all of the necessary configuration to the edge router on my home
network.

group_vars/dch-gw/radvd.yml

@@ -0,0 +1,11 @@
+radvd_interfaces:
+- interface: '{{ dch_networks.jazz.router_iface }}'
+  prefix: '::/64'
+  rdnss: '{{ dch_networks.jazz.dns_servers }}'
+  dnssl: '{{ dch_networks.jazz.dns_search }}'
+
+- interface: '{{ dch_networks.blue.router_iface }}'
+  prefix: '::/64'
+
+- interface: '{{ dch_networks.red.router_iface }}'
+  prefix: '::/64'