Add ability to hide individual weapon usage entries

[daliin]

I often want to hide usages for weapons that involve skills I don't have. For example, if my character doesn't have the Main-Gauche skill, I don't need to see those entries in the Melee Weapon table for all of my knives. Currently I just delete those entries, but sometimes I add the skill later, and then I have to either replace the equipment or manually add the usages again. This isn't too onerous, but sometimes weapons get pretty complicated (with enchantments and other features), so I would prefer being able to just click a checkbox (or a contextual menu option) to toggle them on and off.