add static property WPage::$DEFAULT_SORT_KEY (v 1.4.0 needs 2.8.4)

* fix object's static properties and constants v 2.8.0
* add WTitle properties subjectNsNumber and talkNsNumber


Change-Id: I065b67516e7546f67e3ef5b1721c20a864e464d0
Merge "add static property WPage::$DEFAULT_SORT_KEY (v 1.4.0 needs 2.8.4)"