RFR: 8237503: Update copyright header for files modified in 2020

[Kevin Rushforth]

Fix for [JDK-8237503](https://bugs.openjdk.java.net/browse/JDK-8237503) to update the "last modified" year in the copyright header for all files modified in 2020 in the `jfx14` branch.

NOTE: I'll update this to pick up any last-minute changes integrated to `jfx14` and then remove the WIP.

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Commits:
 - f6dfbd83: Pickup additional files from recent commits
 - b9e40bbc: Merge remote-tracking branch 'upstream/jfx14' into 8237503-copyr-2020
 - 15ca17c2: 8237503: Update copyright header for files modified in 2020

Changes: https://git.openjdk.java.net/jfx/pull/103/files
 Webrev: https://webrevs.openjdk.java.net/jfx/103/webrev.00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8237503
  Stats: 53 lines in 53 files changed: 0 ins; 0 del; 53 mod
  Patch: https://git.openjdk.java.net/jfx/pull/103.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/103/head:pull/103

PR: https://git.openjdk.java.net/jfx/pull/103