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/persistence.lua

@@ -0,0 +1,75 @@
+module 'aux.util.persistence'
+
+local T = require 'T'
+local aux = require 'aux'
+
+function M.read(schema, str)
+    if schema == 'string' then
+        return str
+    elseif schema == 'boolean' then
+        return str == '1'
+    elseif schema == 'number' then
+        return tonumber(str)
+    elseif type(schema) == 'table' and schema[1] == 'list' then
+        return T.temp-read_list(schema, str)
+    elseif type(schema) == 'table' and schema[1] == 'tuple' then
+        return T.temp-read_tuple(schema, str)
+    else
+        error('Invalid schema.', 2)
+    end
+end
+
+function M.write(schema, obj)
+    if schema == 'string' then
+        return obj or ''
+    elseif schema == 'boolean' then
+        return obj and '1' or '0'
+    elseif schema == 'number' then
+        return obj and tostring(obj) or ''
+    elseif type(schema) == 'table' and schema[1] == 'list' then
+        return write_list(schema, obj)
+    elseif type(schema) == 'table' and schema[1] == 'tuple' then
+        return write_tuple(schema, obj)
+    else
+        error('Invalid schema.', 2)
+    end
+end
+
+function read_list(schema, str)
+    if str == '' then return T.acquire() end
+    local separator = schema[2]
+    local element_type = schema[3]
+    return aux.map(aux.split(str, separator), function(part)
+        return read(element_type, part)
+    end)
+end
+
+function write_list(schema, list)
+    local separator = schema[2]
+    local element_type = schema[3]
+    local parts = aux.map(T.temp-aux.copy(list), function(element)
+        return write(element_type, element)
+    end)
+    return aux.join(parts, separator)
+end
+
+function read_tuple(schema, str)
+    local separator = schema[2]
+    local tuple = T.acquire()
+    local parts = T.temp-aux.split(str, separator)
+    for i = 3, getn(schema) do
+        local key, type = next(schema[i])
+        tuple[key] = read(type, parts[i - 2])
+    end
+    return tuple
+end
+
+function write_tuple(schema, tuple)
+    local separator = schema[2]
+    local parts = T.temp-T.acquire()
+    for i = 3, getn(schema) do
+        local key, type = next(schema[i])
+        tinsert(parts, write(type, tuple[key]))
+    end
+    return aux.join(parts, separator)
+end