RFR: 6636: Adding spotless for core

[Marcus Hirt]

This is a test for adding spotless. After this change you can run mvn spotless:check in core, to see that everything is formatted ok. If it fails, you can run mvn spotless:apply, which will format your source automatically for you. If everyone is happy with spotless, I will make spotless available for all code in JMC, and make spotless checks part of the integration checks.

If there are any changes we'd like to do to the formatting template, now would be the time to make them. ;)

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Commits:
 - 933b0d7f: Adding spotless for core

Changes: https://git.openjdk.java.net/jmc/pull/5/files
 Webrev: https://webrevs.openjdk.java.net/jmc/5/webrev.00
  Issue: https://bugs.openjdk.java.net/browse/JMC-6636
  Stats: 331 lines in 48 files changed: 99 ins; 45 del; 187 mod
  Patch: https://git.openjdk.java.net/jmc/pull/5.diff
  Fetch: git fetch https://git.openjdk.java.net/jmc pull/5/head:pull/5

PR: https://git.openjdk.java.net/jmc/pull/5