Implement 'smarter' notched/notchwidth default

I deliberately removed `"notched":true` in one of test
box traces so it is (indirectly) tested

Author: krassowski

src/traces/box/attributes.js

@@ -87,7 +87,6 @@ module.exports = {
     },
     notched: {
         valType: 'boolean',
-        dflt: false,
         role: 'style',
         editType: 'calcIfAutorange',
         description: [

src/traces/box/defaults.js

@@ -29,7 +29,7 @@ function supplyDefaults(traceIn, traceOut, defaultColor, layout) {
     coerce('whiskerwidth');
     coerce('boxmean');
 
-    var notched = coerce('notched');
+    var notched = coerce('notched', traceIn.notchwidth !== undefined);
     if(notched) coerce('notchwidth');
 
     handlePointsDefaults(traceIn, traceOut, coerce, {prefix: 'box'});

test/image/mocks/box_notched.json

@@ -144,7 +144,6 @@
          },
          "type":"box",
          "name":"Notch width = 0.8",
-         "notched":true,
          "notchwidth":0.8
       },
       {