Add new notify type that allows watching of new patch sets

Users can now watch the creation of new patch sets. They get notified
if a new patch set is uploaded, but also if a rebase is done from the
WebUI or the commit message is edited in the WebUI.

Change-Id: Ieabc4c00d2b185e5b452ac43706cb0fdd9d87f77
Signed-off-by: Edwin Kempin <edwin.kempin@sap.com>

gerrit-server/src/main/java/com/google/gerrit/server/mail/CreateChangeSender.java

@@ -70,6 +70,8 @@ public class CreateChangeSender extends NewChangeSender {
       // who have a lower interest in the change.
       log.warn("Cannot notify watchers for new change", err);
     }
+
+    includeWatchers(NotifyType.NEW_PATCHSETS);
   }
 
   private boolean isOwnerOfProjectOrBranch(Account.Id user) {