- I made human/handle_blood() less shitty.

- We no longer leave a blood trail if blood_volume is below a certain level which depends on the brute damage received. This way dragging a wounded player does have a bad effect.
- We no longer give humans a second reagents var containing blood, and we don't put exotic blood in the mob's reagents. Now we don't store any blood substance inside the mob, we only have a blood_volume var. When we draw blood with syringe we create the reagent that match the type (blood reagent, or an exotic blood reagent)
- can't draw blood from mob if it's low on blood, so we can't empty a mob of its blood entirely.
- Removed the blood type preference appearing in character setting.
- blood pack automatically show blood type, unless manually labeled.
- removed bloody_hands_mob human var and same name glove var.
- Some animals now have blood (pets, goat, cows)
- hitting and dragging mobs with actual blood in their veins leaves blood on you and a trail on the floor.
- probably other stuff that I'll mention in the PR.

code/modules/client/preferences.dm

@@ -47,7 +47,6 @@ var/list/preferences_datums = list()
 	var/be_random_body = 0				//whether we'll have a random body every round
 	var/gender = MALE					//gender of character (well duh)
 	var/age = 30						//age of character
-	var/blood_type = "A+"				//blood type (not-chooseable)
 	var/underwear = "Nude"				//underwear type
 	var/undershirt = "Nude"				//undershirt type
 	var/socks = "Nude"					//socks type
@@ -92,7 +91,6 @@ var/list/preferences_datums = list()
 	var/list/ignoring = list()
 
 /datum/preferences/New(client/C)
-	blood_type = random_blood_type()
 	custom_names["ai"] = pick(ai_names)
 	custom_names["cyborg"] = pick(ai_names)
 	custom_names["clown"] = pick(clown_names)
@@ -190,7 +188,6 @@ var/list/preferences_datums = list()
 			else
 				dat += "<b>Species:</b> Human<BR>"
 
-			dat += "<b>Blood Type:</b> [blood_type]<BR>"
 			dat += "<b>Underwear:</b><BR><a href ='?_src_=prefs;preference=underwear;task=input'>[underwear]</a><BR>"
 			dat += "<b>Undershirt:</b><BR><a href ='?_src_=prefs;preference=undershirt;task=input'>[undershirt]</a><BR>"
 			dat += "<b>Socks:</b><BR><a href ='?_src_=prefs;preference=socks;task=input'>[socks]</a><BR>"
@@ -1192,7 +1189,6 @@ var/list/preferences_datums = list()
 
 	character.backbag = backbag
 
-	character.dna.blood_type = blood_type
 	character.dna.features = features.Copy()
 	character.dna.real_name = character.real_name
 	var/datum/species/chosen_species