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.

src/script/functions/construction.cpp

@@ -19,6 +19,7 @@
 #include <data/game.hpp>
 #include <data/stylesheet.hpp>
 #include <data/card.hpp>
+#include <util/uid.hpp>
 #include <util/error.hpp>
 
 // ----------------------------------------------------------------------------- : new_card
@@ -168,9 +169,20 @@ SCRIPT_FUNCTION(add_card_to_set) {
   SCRIPT_RETURN(false);
 }
 
+SCRIPT_FUNCTION(new_uid) {
+  SCRIPT_PARAM_C(Set*, set);
+  String uid = generate_uid();
+  for (int i = 0; i < 100; i++) {
+    if (set->card_uids.find(uid) == set->card_uids.end()) break;
+    uid = generate_uid();
+  }
+  SCRIPT_RETURN(uid);
+}
+
 // ----------------------------------------------------------------------------- : Init
 
 void init_script_construction_functions(Context& ctx) {
   ctx.setVariable(_("new_card"), script_new_card);
+  ctx.setVariable(_("new_uid"), script_new_uid);
   ctx.setVariable(_("add_card_to_set"), script_add_card_to_set);
 }