aux auto bid and price heuristics

this commit does two things
1. it implements auto bid just like auto buy
2. it has some minimum pricing heuristics when posting items. this behavoiur actiaves when the post bid price is set to 0, the buyout price behaves like a minimum

aux-addon/util/sort.lua

@@ -0,0 +1,30 @@
+module 'aux.util.sort'
+
+local T = require 'T'
+
+M.EQ = 0
+M.LT = 1
+M.GT = 2
+
+function M.compare(a, b, desc)
+    if a < b then
+        return desc and GT or LT
+    elseif a > b then
+        return desc and LT or GT
+    else
+        return EQ
+    end
+end
+
+M.multi_lt = T.vararg-function(arg)
+	for i = 1, getn(arg), 2 do
+        if arg[i] and arg[i + 1] and arg[i] ~= arg[i + 1] then
+            return arg[i] < arg[i + 1]
+        elseif not arg[i] and arg[i + 1] then
+            return true
+        elseif not arg[i + 1] then
+            return false
+        end
+	end
+	return false
+end