Nutrition fixes and tweaks (#1265)

Fixes nutrition displays not updating.

Adds code support for species-variable levels of max nutrition storage, and nutrition loss. No actual variations are yet implemented, awaiting input from lore team.

Fixes all relevant static isntances of numeric literals with the max_nutrition variable

And a feature tweak: Players will now spawn with randomised nutrition levels when they join

code/datums/diseases/advance/symptoms/weight.dm

@@ -33,7 +33,7 @@ Bonus
 				M << "<span class='notice'>[pick("You feel blubbery.", "You feel full.")]</span>"
 			else
 				M.overeatduration = min(M.overeatduration + 100, 600)
-				M.nutrition = min(M.nutrition + 100, 500)
+				M.nutrition = min(M.nutrition + 100, M.max_nutrition * 1.25)
 
 	return
 
@@ -114,6 +114,6 @@ Bonus
 		switch(A.stage)
 			if(4, 5)
 				M.overeatduration = 0
-				M.nutrition = 400
+				M.nutrition = M.max_nutrition
 
 	return