Add ability to set reference points relative to hostile/unfriendly/unknown units

[DmitriyBlade]

If contact w/unit is lost, or estimated more than 1 nm
just leave reference point as it stayed before

Echo — 12/17/2021
This would be a good feature to add, I try to set fixed reference points to enemy DDGs for my MPAs to stick to so I can constantly have them illuminated without having to micromanage to keep them out of SAM range.

Now if you set reference points to hostile ship as "fixed", relative drops after few seconds