Allow the player to return with more merch to pay the merchant for cl…

…eanup help.

Previously if the player wasn't carrying any Merch, they could be
flagged as having asked the front-merchant for help with Boris' cleanup
effort, and be told they could "sweeten the deal", but could then never
actually purchase help because the option would not show again.

This commit moves setting the `cleanup_asked` var to when payment is
actually made, and adds a "I might come back with some more Merch…"
dialog option to help guide the player.

Unfortunately this does not fix the quest for players who have already
spoken to the merchant without any Merch.

data/json/npcs/refugee_center/surface_staff/NPC_free_merchant_shopkeep.json

@@ -469,7 +469,6 @@
     "type": "talk_topic",
     "id": "TALK_EVAC_MERCHANT_Boris_Mission_1",
     "dynamic_line": "Hmm.  Most of the people downstairs aren't willing to come up for things like that.  If you sweeten the pot a bit, we could get a few folks I'm sure.",
-    "speaker_effect": { "effect": { "npc_add_var": "cleanup_asked", "type": "mission", "context": "Boris_mission_1", "value": "yes" } },
     "responses": [
       {
         "text": "How about five Merch to do it?",
@@ -482,18 +481,24 @@
         "condition": { "u_has_items": { "item": "FMCNote", "count": 10 } },
         "effect": { "u_adjust_var": "Boris_mission_1", "type": "mission", "context": "cleanup_promises", "adjustment": 3 },
         "topic": "TALK_EVAC_MERCHANT_Boris_Mission_1c"
+      },
+      {
+        "text": "I might come back with some more Merch then…",
+        "topic": "TALK_EVAC_MERCHANT"
       }
     ]
   },
   {
     "type": "talk_topic",
     "id": "TALK_EVAC_MERCHANT_Boris_Mission_1b",
-    "dynamic_line": "Sure.  Five Merch is definitely enough to get someone off guard duty to help you out."
+    "dynamic_line": "Sure.  Five Merch is definitely enough to get someone off guard duty to help you out.",
+    "speaker_effect": { "effect": { "npc_add_var": "cleanup_asked", "type": "mission", "context": "Boris_mission_1", "value": "yes" } }
   },
   {
     "type": "talk_topic",
     "id": "TALK_EVAC_MERCHANT_Boris_Mission_1c",
-    "dynamic_line": "Woah, you're really intent hey?  Okay, if you feel so strongly, ten Merch is enough to get a couple people out of guard duty to help, and you know what?  If you feel that strongly about it, I'll come help out in my down time too.  I respect someone putting their money where their mouth is."
+    "dynamic_line": "Woah, you're really intent hey?  Okay, if you feel so strongly, ten Merch is enough to get a couple people out of guard duty to help, and you know what?  If you feel that strongly about it, I'll come help out in my down time too.  I respect someone putting their money where their mouth is.",
+    "speaker_effect": { "effect": { "npc_add_var": "cleanup_asked", "type": "mission", "context": "Boris_mission_1", "value": "yes" } }
   },
   {
     "id": "MISSION_FREE_MERCHANTS_EVAC_1",