replace 'emptybox' with 'empty' in box calc item

... in preparation for violin

Author: etpinard

src/traces/box/calc.js

@@ -125,7 +125,7 @@ module.exports = function calc(gd, trace) {
         fullLayout[numKey]++;
         return cd;
     } else {
-        return [{t: {emptybox: true}}];
+        return [{t: {empty: true}}];
     }
 };
 

src/traces/box/plot.js

@@ -59,7 +59,7 @@ module.exports = function plot(gd, plotinfo, cdbox) {
         // whisker width
         var wdPos = bdPos * trace.whiskerwidth;
 
-        if(trace.visible !== true || t.emptybox) {
+        if(trace.visible !== true || t.empty) {
             d3.select(this).remove();
             return;
         }

src/traces/box/set_positions.js

@@ -44,7 +44,7 @@ module.exports = function setPositions(gd, plotinfo) {
             trace = cd[0].trace;
 
             if(trace.visible === true && Registry.traceIs(trace, 'box') &&
-                    !t.emptybox &&
+                    !t.empty &&
                     trace.orientation === orientation &&
                     trace.xaxis === xa._id &&
                     trace.yaxis === ya._id) {