Rename properties Layout.{vertical}SizePolicy

..to Layout.fill{Width,Height}

This property now takes a bool, which enables you to write
  Layout.fillWidth: true

instead of
  Layout.horizontalSizePolicy: Layout.Expanding

Change-Id: Icf2e0dc4757938489908b8997d6c4e80c8be1c50
Reviewed-by: Jens Bache-Wiig <jens.bache-wiig@digia.com>