Kill assists assignments should survive across docking/reloading and leaving sector.

Currently kill assist assignments/stats only are given if you have caused damage to a vessel and have not left the sector. This is unbalanced since you can literally just cause 1 damage to any vessel and then turbo out into open space and let it be killed by someone else, but if you cause 99.99999% of damage and then are killed, and the vessel is destroyed before you can return and deal additional damage, you get no assist credit.

This is exacerbated by the sector reset when you play alone.