Begin saving the EppResource parent in *History objects (#1090)

* Begin saving the EppResource parent in *History objects

We use DomainCreateFlow as an example here of how this will work. There
were a few changes necessary:

- various changes around GracePeriod / GracePeriodHistory so that we can
actually store them without throwing NPEs
- Creating one injectable *History.Builder field and using in place of
the HistoryEntry.Builder injected field in DomainCreateFlow
- Saving the EppResource as the parent in the *History.Builder setParent
calls
- Converting to/from HistoryEntry/*History classes in
DatastoreTransactionManager. Basically, we'll want to return the
*History subclasses (and similar in the ofy portions of HistoryEntryDao)
- Converting a few HistoryEntry.Builder usages to DomainHistory.Builder
usages. Eventually we should convert all of them.

core/src/test/resources/google/registry/flows/poll_response_unrenew.xml

@@ -3,7 +3,7 @@
     <result code="1301">
       <msg>Command completed successfully; ack to dequeue</msg>
     </result>
-    <msgQ count="1" id="1-8-TLD-19-20-2001">
+    <msgQ count="1" id="1-9-TLD-20-21-2001">
       <qDate>2001-06-07T00:00:00Z</qDate>
       <msg>Domain example.tld was unrenewed by 3 years; now expires at 2003-06-01T00:02:00.000Z.</msg>
     </msgQ>

core/src/test/resources/google/registry/model/schema.txt

@@ -294,8 +294,8 @@ class google.registry.model.domain.GracePeriod {
   google.registry.model.domain.rgp.GracePeriodStatus type;
   google.registry.persistence.BillingVKey$BillingEventVKey billingEventOneTime;
   google.registry.persistence.BillingVKey$BillingRecurrenceVKey billingEventRecurring;
-  java.lang.Long gracePeriodId;
   java.lang.String clientId;
+  long gracePeriodId;
   org.joda.time.DateTime expirationTime;
 }
 class google.registry.model.domain.Period {