Major organ rewrite. Details in PR. Squashed commit messages:
Migrated brains to obj/item/organ, fixed compile issues, added vars and objects for organ removal, added by-species organ types.
Added placeholder icons for organ removal.
Generalized encased organs and internal organ repair surgery, removed brain_op_status var.
Added PlasmaRifle's organ sprites plus a shitty codersprite for eyeballs.
Continued work on newsurgery. Added organ removal/replacement, added a shit ton of null checks for missing organs, restructured some files.
More work. Organs die after a certain amount of time and bleed everywhere, blood has donor's DNA and colour.
Bug fixes and tweaks.
Merge branch 'dev' of https://github.com/Baystation12/Baystation12 into organremoval