Refactors and cleans up item_attack.dm and related mob attack code
Conflicts:
code/_onclick/item_attack.dm
code/game/objects/items.dm
code/modules/mob/living/bot/bot.dm
code/modules/mob/living/carbon/human/human_defense.dm
code/modules/mob/living/living_defense.dm
code/modules/mob/living/simple_animal/simple_animal.dm