Introduce setting for a max height level for towns

Prior to this change, the game tended to place towns on mountain tops. Realistic heightmaps had limitations because of this.

This change allows the player to specify that the towns should be generated in the valleys.

src/table/settings.ini

@@ -939,10 +939,24 @@ strhelp  = STR_CONFIG_SETTING_TOWN_CARGOGENMODE_HELPTEXT
 strval   = STR_CONFIG_SETTING_TOWN_CARGOGENMODE_ORIGINAL
 cat      = SC_ADVANCED
 
-;; economy.max_town_heightlevel
-[SDT_NULL]
-length   = 1
+[SDT_XREF]
 extver   = SlXvFeatureTest(XSLFTO_AND, XSLFI_JOKERPP)
+xref     = ""economy.max_town_heightlevel""
+
+[SDT_VAR]
+base     = GameSettings
+var      = economy.max_town_heightlevel
+type     = SLE_UINT8
+guiflags = SGF_NEWGAME_ONLY | SGF_SCENEDIT_TOO
+def      = MAX_MAP_HEIGHT_LIMIT
+min      = 4
+max      = MAX_MAP_HEIGHT_LIMIT
+interval = 1
+str      = STR_CONFIG_SETTING_TOWN_ABOVE_HEIGHT
+strhelp  = STR_CONFIG_SETTING_TOWN_ABOVE_HEIGHT_HELPTEXT
+strval   = STR_JUST_INT
+cat      = SC_BASIC
+patxname = ""max_town_heightlevel.economy.max_town_heightlevel""
 
 ; link graph