eventLogging: Add missing *Hover properties
- Include the namespace ID in LINK_DWELL.
- Add the createEvent helper, which adds the pageTitleHover and namespaceIdHover properties in the event.
- Create "dismissed", "dwelledButAbandoned", and "opened" events using the createEvent helper.
- Store the target page's associated mw.Title using jQuery.
- Update the eventLogging reducer's test cases so that all LINK_DWELL representations include title and namespaceID attributes.
- Create the createStubTitle factory function, which returns a minimal usable mw.Title stub, and use it in the actions and integration test cases.