[NEXUS-6687] make timestamp millis, add atom-long based sequence to de-dup
[NEXUS-6687] bring back rolling counter for sequence.  make duration nanos again.  update ui and persistence for new field.
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Merge pull request #623 from sonatype/NEXUS-6687-timestamp-millis-sequence-counter-master

[NEXUS-6687] (master) make timestamp millis, add sequence