Draw a vessel of unknown length at its ship type's typical size

Most live vessel feeds send no length, and the resolver then fell through
every length rule to the range's last model drawn as built, so a cruise
ship or a container ship showed as the smallest model of its range.
types.json gives each passenger, cargo, tanker, fishing and service range
a typical_len (cargo 300 m, tanker 250 m, passenger 140 m, fishing 40 m,
...); a vessel with no usable length is chosen and drawn at it.

public/models/fleet/types.json

@@ -1149,6 +1149,7 @@
     70,
     79
    ],
+   "typical_len": 300,
    "rules": [
     {
      "min_len": 70,
@@ -1188,6 +1189,7 @@
     80,
     89
    ],
+   "typical_len": 250,
    "rules": [
     {
      "name_re": "\\bLNG\\b|\\bGAS\\b",
@@ -1214,6 +1216,7 @@
     60,
     69
    ],
+   "typical_len": 140,
    "rules": [
     {
      "min_len": 70,
@@ -1243,6 +1246,7 @@
     37,
     37
    ],
+   "typical_len": 19,
    "rules": [
     {
      "min_len": 35,
@@ -1273,6 +1277,7 @@
     30,
     30
    ],
+   "typical_len": 24,
    "rules": [
     {
      "min_len": 15,
@@ -1343,6 +1348,7 @@
     55,
     55
    ],
+   "typical_len": 40,
    "rules": [
     {
      "min_len": 25,
@@ -1358,6 +1364,7 @@
     40,
     49
    ],
+   "typical_len": 40,
    "rules": [
     {
      "min_len": 20,
@@ -1373,6 +1380,7 @@
     33,
     33
    ],
+   "typical_len": 100,
    "rules": [
     {
      "min_len": 50,