add new_uid script function

doc/function/index.txt

@@ -109,6 +109,7 @@ These functions are built into the program, other [[type:function]]s can be defi
 	
 ! Cards				<<<
 | [[fun:new_card]]		Construct a new [[type:card]] object.
+| [[fun:new_uid]]		Construct a new uid.
 | [[fun:add_card_to_set]]		Add a [[type:card]] to a [[type:set]].
 | [[fun:get_card_styling]]		Get the styling data of a [[type:card]].
 | [[fun:get_card_stylesheet]]	Get the stylesheet of a [[type:card]].

doc/function/new_uid.txt

@@ -0,0 +1,10 @@
+Function: new_uid
+
+--Usage--
+> new_uid()
+
+Returns a new card uid, a string of 32 random digits, which is guaranteed to not exist in the set.
+
+--Parameters--
+! Parameter	Type				Description
+| @set@		[[type:set]]		The set in which to look for uid conflicts. This can be omitted since 'set' is a predefined variable.