Allowing seed number to save onto exported yaml if provided by user

source/classes/CustomSettings.py

@@ -271,6 +271,8 @@ class CustomSettings(object):
         self.player_range = range(1, world.players + 1)
         settings_dict, meta_dict = {}, {}
         self.world_rep['meta'] = meta_dict
+        if world.seed:
+            meta_dict['seed'] = world.seed
         meta_dict['players'] = world.players
         meta_dict['algorithm'] = world.algorithm
         meta_dict['race'] = settings.race