Show Advisory Speed Limit by default on link presets in Canada, U.S.

Canada and the United States generally post only an advisory speed limit and avoid posting a legal speed limit on highway ramps. Other countries differ. This change splits the maxspeed field into two as a workaround for the inability to limit the default inclusion of a field to a particular location set.

data/presets/golf/cartpath.json

@@ -2,7 +2,8 @@
     "icon": "temaki-golf_cart",
     "fields": [
         "{golf/path}",
-        "maxspeed"
+        "maxspeed",
+        "maxspeed_mutcd"
     ],
     "geometry": [
         "line"