RFR: 8313424: JavaFX controls in the title bar [v38]

[Michael Strauß]

> Implementation of [`EXTENDED`](https://gist.github.com/mstr2/0befc541ee7297b6db2865cc5e4dbd09) and `EXTENDED_UTILITY` stage style.

Michael Strauß has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 49 commits:

 - added custom header buttons
 - Merge branch 'master' into feature/extended-window
 - Refactoring, added HeaderBar.leadingSystemPadding/trailingSystemPadding
 - Merge branch 'master' into feature/extended-window
 - fix resizable states for GTK windows
 - add StageStyle.EXTENDED_UTILITY
 - fix system menu for non-resizeable extended window
 - Merge branch 'master' into feature/extended-window
   
   # Conflicts:
   #	modules/javafx.graphics/src/main/java/com/sun/javafx/tk/quantum/GlassViewEventHandler.java
 - StyleableBooleanProperty -> BooleanProperty
 - Add HeaderBar.overlappingSystemInset property
 - ... and 39 more: https://git.openjdk.org/jfx/compare/a1765747...49a81d32

-------------

Changes: https://git.openjdk.org/jfx/pull/1605/files
  Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1605&range=37
  Stats: 5975 lines in 67 files changed: 4864 ins; 426 del; 685 mod
  Patch: https://git.openjdk.org/jfx/pull/1605.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1605/head:pull/1605

PR: https://git.openjdk.org/jfx/pull/1605