Make submittable a ListChangesOption

Some scripts rely on the submittable bit from QueryChanges to
implement an 'automatically submit when approved to do so' feature,
to allow a person to mark a change as Autosubmit-Ready and go home
for the night in the expectation that a CI system will verify the
change and cause it to be submitted.

4cd05b2c5e (Only compute submittable
during submitted_together, 2016-09-17), which was needed for
performance reasons when rendering dashboards, broke these scripts.
Allow them to work again through a new o=SUBMITTABLE option.

Change-Id: Ia6ce6d95b1d774ede786b797eb04ce1353de6c86

gerrit-server/src/main/java/com/google/gerrit/server/change/SubmittedTogether.java

@@ -54,7 +54,8 @@ public class SubmittedTogether implements RestReadView<ChangeResource> {
 
   private final EnumSet<ListChangesOption> jsonOpt = EnumSet.of(
       ListChangesOption.CURRENT_REVISION,
-      ListChangesOption.CURRENT_COMMIT);
+      ListChangesOption.CURRENT_COMMIT,
+      ListChangesOption.SUBMITTABLE);
 
   private final ChangeJson.Factory json;
   private final Provider<ReviewDb> dbProvider;
@@ -152,9 +153,7 @@ public class SubmittedTogether implements RestReadView<ChangeResource> {
       }
 
       SubmittedTogetherInfo info = new SubmittedTogetherInfo();
-      info.changes = json.create(jsonOpt)
-        .includeSubmittable(true)
-        .formatChangeDatas(cds);
+      info.changes = json.create(jsonOpt).formatChangeDatas(cds);
       info.nonVisibleChanges = hidden;
       return info;
     } catch (OrmException | IOException e) {