vm: add default admin pages

circle/vm/admin.py

+from django.contrib import admin
+
+from .models import (Node, InstanceTemplate, InterfaceTemplate, Instance,
+                     InstanceActivity, NodeActivity)
+
+
+admin.site.register(Node)
+admin.site.register(InstanceTemplate)
+admin.site.register(InterfaceTemplate)
+admin.site.register(Instance)
+admin.site.register(InstanceActivity)
+admin.site.register(NodeActivity)