NEWT Window: Remove deprecated methods: HiDPI + reparentWindow(..)

Remove HiDPI pixel- from/to window-unit conversion and getter methods:
  Rectangle HiDPI pixel- from/to window-units are erroneous in case of multiple monitor setup where a mixed pixel-scale exist,
  since the methods didn't take the monitor viewport and each of it's pixel-scale into account (expensive).

Remove deprecated reparentWindow(..) methods.
Bug 741 HiDPI: Add ScalableSurface.getNativeSurfaceScale(..) to compute surface DPI ; Add NEWT Window.getPixelsPerMM(..) to query surface DPI

With HiDPI and surface scale, we need knowledge of the native surface's pixel-scale
matching the monitor's pixel-per-millimeter value.

Preserving the queried native pixel-scale and exposing it via
ScalableSurface.getNativeSurfaceScale(..) to compute surface DPI.

Add NEWT Window.getPixelsPerMM(..) to query surface DPI.

Surface DPI is demonstrated in GraphUI's GPUUISceneGLListener0A .. and TestRulerNEWT01, etc ..