resources: net: Add net resource

This patch adds a net resource for managing nework interfaces, based
around netlink.

examples/lang/net1.mcl

@@ -0,0 +1,5 @@
+net "eth0" {
+	state => "up",
+	addrs => ["192.168.42.13/24",],
+	gateway => "192.168.42.1",
+}

examples/lang/net2.mcl

@@ -0,0 +1,3 @@
+net "eth0" {
+	state => "up",
+}

examples/lang/net3.mcl

@@ -0,0 +1,3 @@
+net "eth0" {
+	state => "down",
+}