Add IPv6 Interface Support

Add IPv6 Interface Support
First Version

README.rst

             - 8.8.4.4
             mtu: 1500
 
+
+Linux with IPv4 and IPv6 static network interfaces, default gateway
+
+            .. code-block:: yaml
+
+                linux:
+                  network:
+                    enabled: true
+                    interface:
+                      eth0:
+                        enabled: true
+                        type: eth
+                        address: 192.168.0.102
+                        netmask: 255.255.255.0
+                        gateway: 192.168.0.1
+
+                        enable_ipv6: true
+                        ipv6proto: static
+                        ipv6ipaddr:  1234:abcd::ffff:192.168.0.102
+                        ipv6gateway: 1234:abcd::ffff:192.168.0.1
+                        ipv6netmask: 64
+
+
 Linux with bonded interfaces and disabled ``NetworkManager``:
 
 .. code-block:: yaml

linux/network/interface.sls

   {%- else %}
   - proto: {{ interface.get('proto', 'dhcp') }}
   {%- endif %}
+
+  # IPv6
+  {%- if interface.enable_ipv6 is defined %}
+  - enable_ipv6: {{ interface.enable_ipv6 }}
+  {%-   if interface.ipv6ipaddr is defined %}
+  {%-     if grains.os_family == 'Debian' %}
+  - ipv6proto: {{ interface.get('ipv6proto', 'static') }}
+  {%-     endif %}
+  - ipv6ipaddr: {{ interface.ipv6ipaddr }}
+  - ipv6gateway: {{ interface.ipv6gateway }}
+  - ipv6netmask: {{ interface.ipv6netmask }}
+  {%-   endif %}
+  {%- endif %}
+
   {%- if interface.type == 'slave' %}
   - master: {{ interface.master }}
   {%- endif %}