[9] Review request: 8091832: Provide API for getting the Screen scale on HiDPI screens

[Jim Graham]

bug: https://bugs.openjdk.java.net/browse/JDK-8091832
webrev: http://cr.openjdk.java.net/~flar/JDK-8091832/webrev.rt.00/

This webrev fixes pixel snapping and application control over pixel 
scaling on HiDPI screens:

- snap*() methods are all updated to take the current scale into account
- new variants of snap*() methods are added for separate X/Y control:
     Added: Region.snapSpaceX/Y()
     Added: Region.snapSizeX/Y()
     Added: Region.snapPositionX/Y()
- the non-X/Y variants of the above methods are now deprecated:
     Deprecated: Region.snapSpace()
     Deprecated: Region.snapSize()
     Deprecated: Region.snapPosition()
- methods to query the scale values of Screen objects:
     Added: Screen.getOutputScaleX/Y()
- properties to query and/or modify the scale values of Window objects:
     Added Read-Only  DoubleProperty:  Window.getOutputScaleX/Y()
     Added Read-Write BooleanProperty: 
Window.set/getForceIntegerRenderScale()
     Added Read-Write DoubleProperty:  Window.set/getRenderScaleX/Y()

The changes have been compiled and tested on Windows and Mac and there 
were trivial changes needed to the Linux files to adapt to one new 
method signature, but I haven't done the test build on Linux yet...

			...jim