Add ADD_PATCH_SET logic to lock patch sets

I've added a new permission to distinguish between creating a change and
adding new patch sets. This is intended for projects that want to
restrict the upload of new patch sets to the change owner (or any other
group).

Change-Id: If9f9f7ed0f0890fb4b854d0bf71e546ebe43ef96

gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/git/AbstractPushForReview.java

@@ -429,7 +429,8 @@ public abstract class AbstractPushForReview extends AbstractDaemonTest {
         PushOneCommit.SUBJECT, "b.txt", "anotherContent", r.getChangeId());
     revision(r).review(new ReviewInput().label("Patch-Set-Lock", 1));
     r = push.to("refs/for/master");
-    r.assertErrorStatus("cannot replace " + r.getChange().change().getChangeId()
+    r.assertErrorStatus("cannot add patch set to "
+        + r.getChange().change().getChangeId()
         + ". Change is patch set locked.");
   }