Adds Modifier System, Changes Some Ling Stuff

Adds a fairly simple system that allows adjusting various numbers like max health, incoming damage, outgoing melee damage, etc.  The nice part is that changing certain variables this way (like max health) is a lot safer than manually setting the max health var directly.
Changes a lot of short lines of code to point towards a variable's getter or setter helper instead of reading the var directly so the modifiers can work.
Endoarmor, delayed toxin sting, Enfeebling sting, and recursive adrenaline overdose now use the modifier system.
Enfeebling sting now only lasts two minutes, from five minutes, however it now also reduces the victim's melee damage by 25%/50%, and increases the damage they suffer by 10%/35%, for normal and recursive respectively.
Delayed Toxin Sting's effects are now felt all at once instead of over the course of a few minutes.

code/modules/xenobio2/machinery/injector_computer.dm

@@ -76,7 +76,7 @@
 
 	if(injector.occupant)
 		data["occupantHealth"] = injector.occupant.health
-		data["occupantHealthMax"] = injector.occupant.maxHealth
+		data["occupantHealthMax"] = injector.occupant.getMaxHealth()
 	else
 		data["occupantHealth"] = null
 		data["occupantHealthMax"] = null