Take class A/B into account when asigning messages to segments

[pwoods25443]

breaking this out from #24

Here is a nice example of two vessels with the same MMSI being combined when it is clear that there is a class A vessel and a class B vessel. These should be easy to separate

WITH messages_segmented as (
  select 
    source,
    type,
    ssvid,
    timestamp,
    shipname,
    callsign,
    lat,
    lon,
    seg_id
  from `pipe_production_b.messages_segmented_201811*` 
)

select * from messages_segmented
where ssvid in ("412331077") 
order by timestamp

LIMIT 1000

Note the type 18 message that appears at 2018-11-02 03:43:19 UTC is from a different vessel