Dog AI 2.0 (#57186)

Now that JPS and AI movement datums are fully merged, I'm here to take another (my third actually) crack at giving dogs fun AI. Here's a video demonstration (somewhat WIP), and a quick rundown of everything dogs will be able to do. Basically all of these behaviors are generic and can be extended to other simple mobs,
Commands and Friendship
Fetching
Attack/Harass
Heel
Play Dead

code/controllers/subsystem/throwing.dm

@@ -188,6 +188,9 @@ SUBSYSTEM_DEF(throwing)
 		if(T && thrownthing.has_gravity(T))
 			T.zFall(thrownthing)
 
+	if(thrownthing)
+		SEND_SIGNAL(thrownthing, COMSIG_MOVABLE_THROW_LANDED, src)
+
 	qdel(src)
 
 /datum/thrownthing/proc/hit_atom(atom/A)