Gameplay: add option to delete unwanted items from personal footlocker

[Badziew]

Problem:
When someone gives items to you AND you are in faction stronghold AND you are overloaded, the gifts are automatically put in your personal footlocker.
This mechanic could theoretically be used to grief people by filling their inventory with junk items, forcing them to waste AP to take the junk out.

Solution:
Add option to delete unwanted items from footlocker for free (costing zero AP).
Deleted items are (of course) permanently removed from game, and there should be checks to prevent deleting items that cannot normally be dropped/removed (e.g. credit store items).