Adds a Trait system (#4048)

* Works on trait system, wip.

* Finalizes traits.
Fixes a few bugs with medical machines assuming a max health of 100.

code/datums/mind.dm

@@ -68,6 +68,9 @@
 	//used for optional self-objectives that antagonists can give themselves, which are displayed at the end of the round.
 	var/ambitions
 
+	//used to store what traits the player had picked out in their preferences before joining, in text form.
+	var/list/traits = list()
+
 /datum/mind/New(var/key)
 	src.key = key