Change: rename setting "max_heightlevel" to "map_height_limit"

This better reflects what it is, and hopefully removes a bit of
the confusion people are having what this setting actually does.

Additionally, update the text on the setting to better inform
users what it is doing exactly, so they can make an educated
decision on how to change it.

Next commit will introduce an "auto" value, which should be the
new default. The rename has as added benefit that everyone will
start out on the "auto" value.

src/table/settings.ini

@@ -391,16 +391,16 @@ cat      = SC_BASIC
 
 [SDT_VAR]
 base     = GameSettings
-var      = construction.max_heightlevel
+var      = construction.map_height_limit
 type     = SLE_UINT8
 from     = SLV_194
 guiflags = SGF_NEWGAME_ONLY | SGF_SCENEDIT_TOO
-def      = DEF_MAX_HEIGHTLEVEL
-min      = MIN_MAX_HEIGHTLEVEL
-max      = MAX_MAX_HEIGHTLEVEL
+def      = DEF_MAP_HEIGHT_LIMIT
+min      = MIN_MAP_HEIGHT_LIMIT
+max      = MAX_MAP_HEIGHT_LIMIT
 interval = 1
-str      = STR_CONFIG_SETTING_MAX_HEIGHTLEVEL
-strhelp  = STR_CONFIG_SETTING_MAX_HEIGHTLEVEL_HELPTEXT
+str      = STR_CONFIG_SETTING_MAP_HEIGHT_LIMIT
+strhelp  = STR_CONFIG_SETTING_MAP_HEIGHT_LIMIT_HELPTEXT
 strval   = STR_JUST_INT
 proc     = ChangeMaxHeightLevel
 cat      = SC_BASIC