Add support for a domain transfer request superuser EPP extension

Allow superusers to change the transfer period to zero years and allow
superusers to change the automatic transfer length.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=167598314

java/google/registry/flows/EppXmlTransformer.java

@@ -63,7 +63,8 @@ public class EppXmlTransformer  {
       "dsig.xsd",
       "smd.xsd",
       "launch.xsd",
-      "allocate.xsd");
+      "allocate.xsd",
+      "superuser.xsd");
 
   private static final XmlTransformer INPUT_TRANSFORMER =
       new XmlTransformer(SCHEMAS, EppInput.class);