Provide import options for UIA/UIP to make the imported files more designer friendly

UIA import generates Window root component for the top level qml and presentation qmls are not usable outside the context of the top level qml due to relative import paths. For design studio, this top level Window component is not needed, so presentations should be on the top level directory. Also, scenes should be at least optionally separated to their own components so you can use just them in your own View3D item.

So the following options should be provided (default value in parentheses):

• Create top level Window component for UIA import (false)
  • When no Window component is created, presentation components should be created on top level
• Create container component for presentations (false)
  • This means the Rectangles containing View3D
• Create separate scene components for presentations (true)