Update mw.api.watch according to new Watch API

* Using titles instead of title which is deprecated
* Allow operation on multiple pages
Follow up of I820dcb64d469616b10741df013911197cc5bde29

Change-Id: Ic77b546c256fa70f253c7508defe4c0002258b2a
Merge "Update mw.api.watch according to new Watch API"