RFR: 8295729: Add jcheck whitespace checking for properties files

[Magnus Ihse Bursie]

Properties files is essentially source code. It should have the same whitespace checks as all other source code, so we don't get spurious trailing whitespace changes.

With the new Skara jcheck, it is possible to increase the coverage of the whitespace checks (in the old mercurial version, this was more or less impossible).

The only manual change is to `.jcheck/conf`. All other changes were made by running `find . -type f -iname "*.properties" | xargs gsed -i -e 's/[ \t]*$//'`.

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Commit messages:
 - 8295729: Add jcheck whitespace checking for properties files

Changes: https://git.openjdk.org/jdk/pull/10792/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10792&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8295729
  Stats: 1105 lines in 368 files changed: 0 ins; 0 del; 1105 mod
  Patch: https://git.openjdk.org/jdk/pull/10792.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10792/head:pull/10792

PR: https://git.openjdk.org/jdk/pull/10792