switch to regional presets instead of regional fields

also limit to ramps of type motorway, trunk and primary.

data/fields/maxspeed/advisory_mutcd.json

@@ -1,9 +0,0 @@
-{
-    "key": "maxspeed:advisory",
-    "type": "roadspeed",
-    "label": "Advisory Speed Limit",
-    "placeholder": "40, 50, 60...",
-    "locationSet": {
-        "exclude": ["ca", "us"]
-    }
-}

data/fields/maxspeed_mutcd.json

@@ -1,9 +0,0 @@
-{
-    "key": "maxspeed",
-    "type": "roadspeed",
-    "label": "Speed Limit",
-    "placeholder": "40, 50, 60...",
-    "locationSet": {
-        "include": ["ca", "us"]
-    }
-}