RFR: 8367439: Bulk change notifications for ObservableSet and ObservableMap

[Michael Strauß]

Implementation of bulk change notifications for ObservableSet and ObservableMap.

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Commit messages:
 - add tests, documentation
 - Implementation of bulk change listeners for ObservableSet and ObservableMap

Changes: https://git.openjdk.org/jfx/pull/1885/files
  Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1885&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8367439
  Stats: 1193 lines in 13 files changed: 1017 ins; 114 del; 62 mod
  Patch: https://git.openjdk.org/jfx/pull/1885.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1885/head:pull/1885

PR: https://git.openjdk.org/jfx/pull/1885