Optionally auto-deactivate equipment upon archiving

[orenyk]

This is some combination of #1216 and #1118; we probably want to allow certain archiving flags to automatically trigger deactivation of the equipment item (e.g. if the equipment item is lost). I'm not sure how feasible this is for the short-term, so I'm going to add it v6.0.0.

[orenyk]

Woo done with actual TDD and entirely in vim 😄! PR issued, ready for review.