Auction House Limited-Vendor-Item Availability (#212)

The Problem:
The Auction House Bot is intended to mimic real player auction
behavior, which includes selling items commonly farmed and sold
by players.  However, the AH Bot was designed to not sell any
item that an NPC Vendor sells in any quantity. While this makes
sense, it prevents items that any Vendor sells in even very limited
quantities (such as all sorts of Leather) from every being listed.

The Fix:
Better mimic desired player auction behavior by allowing the AH Bot
to sell limited-quantity vendor items by narrowing the general
vendor item restriction to ONLY those items that vendors sell
in unlimited quantities.

The Details:
The AH Bot queries the npc_vendor table to compile a list of items
it will Not list on the AH.  These query results are narrowed by adding
'WHERE maxcount = 0', which will only capture items that vendors
sell in Unlimited quantities, thus allowing Leather to appear on the AH.

Author: bozimmerman

src/game/AuctionHouseBot/AuctionHouseBot.cpp

@@ -1380,7 +1380,7 @@ bool AuctionBotSeller::Initialize()
 
     // Load NPC vendor items for filtering
     sLog.outString("Loading npc vendor items for filter..");
-    if (QueryResult* result = WorldDatabase.Query("SELECT DISTINCT `item` FROM `npc_vendor`"))
+    if (QueryResult* result = WorldDatabase.Query("SELECT DISTINCT `item` FROM `npc_vendor` WHERE `maxcount` = 0"))
     {
         BarGoLink bar(result->GetRowCount());
         do