Update anchorages to work with thinned messages with track_id.
Replace vessel-id with track-id
Rather than a list of vessel-ids, voyages now have a single track-id
Create port-visits even if there is either an exit or an entry event (or both), to avoid some
corner cases where vessels enter a port and aren't seen leaving, or we miss the entry.
Related to https://globalfishingwatch.atlassian.net/browse/PIPELINE-74
Update anchorages to work with thinned messages with
track_id.vessel-idwithtrack-idvessel-ids, voyages now have a singletrack-id