CORD-1345: Rename PlCoreBase to XOSBase

Change-Id: I7c103d9906875a8ba735d6683a5233badaaa6da3
diff --git a/xos/attic/header.py b/xos/attic/header.py
index 6b19427..91b13e7 100644
--- a/xos/attic/header.py
+++ b/xos/attic/header.py
@@ -1,6 +1,6 @@
 from django.db import models
-from core.models import Service, PlCoreBase, Slice, Instance, Tenant, TenantWithContainer, Node, Image, User, Flavor, NetworkParameter, NetworkParameterType, Port, AddressPool, User
-from core.models.plcorebase import StrippedCharField
+from core.models import Service, XOSBase, Slice, Instance, Tenant, TenantWithContainer, Node, Image, User, Flavor, NetworkParameter, NetworkParameterType, Port, AddressPool, User
+from core.models.xosbase import StrippedCharField
 import os
 from django.db import models, transaction
 from django.forms.models import model_to_dict