Repeater & itemviews: fix setModel() JS array handling

QVariant comparison in setModel() started failing because
JS arrays are now passed as a QJSValue. Re-assigning the
same array content should not trigger a model change.

This change restores the old behavior it had before, when
JS arrays were passed as QVariantLists.

Change-Id: I1882b3531f2893b116dbd817edeecab1ae812ce8
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>