Fix layout issues with recently removed items.

Fix layout issues with recently removed items.

Items removed from the source model aren't removed from the cache
group until they've also been released by the view.  Skip over
these removed items when translating future changes to the source
model so no invalid translated changes are created.

Change-Id: I9bf3801135e78b5a6493b4ef50ce44ee5c912bfc
Reviewed-on: http://codereview.qt-project.org/6298
Sanity-Review: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Martin Jones <martin.jones@nokia.com>