RFR: SKARA-971: Stop clumping up logs in logstash

[Erik Joelsson]

I would like to change how we send logs to logstash so each log message is stored as an individual document. To make this more practical, we need to add some more meta data to each message so we can properly filter them. I suggest adding the following:

instance_start_time: An ISO_INSTANT time stamp string indicating when this JVM instance was started.
work_id: A running counter generated ID for each work item, rest request or periodic check, which was previously clumped up in one log message.
work_item: For work items, store the item toString()

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Commit messages:
 - Corrected comment
 - Implemented LogContext

Changes: https://git.openjdk.java.net/skara/pull/1120/files
 Webrev: https://webrevs.openjdk.java.net/?repo=skara&pr=1120&range=00
  Issue: https://bugs.openjdk.java.net/browse/SKARA-971
  Stats: 368 lines in 6 files changed: 134 ins; 197 del; 37 mod
  Patch: https://git.openjdk.java.net/skara/pull/1120.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/1120/head:pull/1120

PR: https://git.openjdk.java.net/skara/pull/1120