Add setting to select cargo payment algorithm

See: #506

src/table/settings/settings.ini

@@ -3237,6 +3237,20 @@ def      = false
 cat      = SC_EXPERT
 patxname = ""economy.disable_inflation_newgrf_flag""
 
+[SDT_VAR]
+var      = economy.payment_algorithm
+type     = SLE_UINT8
+flags    = SF_GUI_DROPDOWN
+def      = CPA_MODERN
+min      = CPA_BEGIN
+max      = CPA_END - 1
+interval = 1
+str      = STR_CONFIG_SETTING_CARGO_PAYMENT_ALGORITHM
+strhelp  = STR_CONFIG_SETTING_CARGO_PAYMENT_ALGORITHM_HELPTEXT
+strval   = STR_CONFIG_SETTING_CARGO_PAYMENT_ALGORITHM_TRADITIONAL
+cat      = SC_BASIC
+patxname = ""economy.payment_algorithm""
+
 ##
 [SDT_VAR]
 var      = pf.wait_for_pbs_path