RFR: 6846: Parser needs to skip events with no metadata

[Marcus Hirt]

Also fixing some javadoc errors.

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Commit messages:
 - Better test naming
 - Correcting copyright
 - 6846: Parser needs to skip events with no metadata

Changes: https://git.openjdk.java.net/jmc/pull/128/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jmc&pr=128&range=00
  Issue: https://bugs.openjdk.java.net/browse/JMC-6846
  Stats: 79 lines in 5 files changed: 70 ins; 1 del; 8 mod
  Patch: https://git.openjdk.java.net/jmc/pull/128.diff
  Fetch: git fetch https://git.openjdk.java.net/jmc pull/128/head:pull/128

PR: https://git.openjdk.java.net/jmc/pull/128