Add lua entity_list function GetShuffledClientList()

There is cases where we need to get a random client, but
GetRandomClient() is not sufficient enough due to complex predicates
required on what tells us is a valid client. This way we can just loop
over a shuffled list and verify a client is valid instead of multiple
GetRandomClient() calls.

zone/lua_entity_list.h

@@ -101,6 +101,7 @@ public:
 	Lua_Client GetRandomClient(float x, float y, float z, float dist, Lua_Client exclude);
 	Lua_Mob_List GetMobList();
 	Lua_Client_List GetClientList();
+	Lua_Client_List GetShuffledClientList();
 	Lua_NPC_List GetNPCList();
 	Lua_Corpse_List GetCorpseList();
 	Lua_Object_List GetObjectList();