RFR: 8290844: Add Skin.install() method [v10]

[Andy Goryachev]

> - added Skin.install()
> - javadoc changes for Skinnable.setSkin(Skin)

Andy Goryachev has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 22 additional commits since the last revision:

 - Merge remote-tracking branch 'origin/master' into 8290844.skin.install
 - 8290844: javadoc
 - Merge branch 'openjdk:master' into 8290844.skin.install
 - 8290844: unit tests
 - Merge remote-tracking branch 'origin/master' into 8290844.skin.install
 - 8290844: review comments
 - 8290844: review comments
 - Merge remote-tracking branch 'origin/master' into 8290844.skin.install
 - 8290844: review comments
 - 8290844: review comments
 - ... and 12 more: https://git.openjdk.org/jfx/compare/9d11e912...6f6b95c0

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Changes:
  - all: https://git.openjdk.org/jfx/pull/845/files
  - new: https://git.openjdk.org/jfx/pull/845/files/d954aafc..6f6b95c0

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=845&range=09
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=845&range=08-09

  Stats: 116 lines in 6 files changed: 84 ins; 8 del; 24 mod
  Patch: https://git.openjdk.org/jfx/pull/845.diff
  Fetch: git fetch https://git.openjdk.org/jfx pull/845/head:pull/845

PR: https://git.openjdk.org/jfx/pull/845