os-networks extension

This commit adds the os-networks extention. This can be used to view
details about the nova-network-based networks that a tenant has access
to.
diff --git a/openstack/compute/v2/extensions/networks/doc.go b/openstack/compute/v2/extensions/networks/doc.go
new file mode 100644
index 0000000..fafe4a0
--- /dev/null
+++ b/openstack/compute/v2/extensions/networks/doc.go
@@ -0,0 +1,2 @@
+// Package network provides the ability to manage nova-networks
+package networks