Use QDeclarativeChangeSet to communicate changes to views.

Use QDeclarativeChangeSet to communicate changes to views.

Allows QSGVisualDataModel to send multiple changes at a time. Changes
sets with multiple changes will be generated by VisualDataModels with
items that have been re-ordered or filtered.

Task-number: QTBUG-20107
Change-Id: I28f2620431cc89c61e1061635ffb68dc5801675c
Reviewed-on: http://codereview.qt-project.org/4034
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Bea Lam <bea.lam@nokia.com>
Reviewed-by: Alan Alpert <alan.alpert@nokia.com>