Adding first-seen/last-seen to dataset with new flags

[codingo]

Whilst the captured data is good, it fails in conditions where there's load balancing in place (as the IP will rotate on each capture).

Suggested fix to this is to add two date fields, first-seen and last-seen, potentially also seen as an integer count (less valuable, nice to have).

As alerts would then change around this, flags should be added:

• fs which would boolean toggle a messaging being shown each run of all first scene items
• ls which would toggle messaging to show if an item was in the last scan, but is no longer seen in days since the specified run. So ls 2 woudl shown any items not seen this run, or in the last two days.
• lsd which is ls, but in US datetime format, showing prompts for items that haven't been seen since lsd <date>

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