[Bars] Option to display totals on top of each bar

Rename option
Refactor code according to comments

Contributes to plotly#85

Author: wilhelmhb

src/traces/bar/layout_attributes.js

@@ -64,16 +64,18 @@ module.exports = {
             'the same location coordinate.'
         ].join(' ')
     },
-    displaytotal: {
+    barshowtotal: {
         valType: 'boolean',
         dflt: false,
         role: 'style',
+        editType: 'plot',
         description: 'Display the total value of each bar.'
     },
     totaltemplate: {
         valType: 'string',
         dflt: '%{total}',
         role: 'style',
+        editType: 'plot',
         description: 'Template to display the total value of each bar.'
     },
 };

src/traces/bar/layout_defaults.js

@@ -55,6 +55,6 @@ module.exports = function(layoutIn, layoutOut, fullData) {
 
     coerce('bargap', (shouldBeGapless && !gappedAnyway) ? 0 : 0.2);
     coerce('bargroupgap');
-    coerce('displaytotal');
-    coerce('totaltemplate');
+    var showTotal = coerce('barshowtotal');
+    if(showTotal) coerce('totaltemplate');
 };

src/traces/bar/plot.js

@@ -298,7 +298,7 @@ function appendBarText(gd, plotinfo, bar, cd, i, x0, x1, y0, y1, opts, makeOnCom
     var isHorizontal = (trace.orientation === 'h');
 
     var text = getText(fullLayout, cd, i, xa, ya);
-    textPosition = getTextPosition(trace, i, fullLayout.displaytotal);
+    textPosition = fullLayout.barshowtotal ? 'inside' : getTextPosition(trace, i);
 
     // compute text position
     var inStackOrRelativeMode =
@@ -673,8 +673,7 @@ function getText(fullLayout, cd, index, xa, ya) {
     return helpers.coerceString(attributeText, value);
 }
 
-function getTextPosition(trace, index, forceInside) {
-    if(forceInside) return 'inside';
+function getTextPosition(trace, index) {
     var value = helpers.getValue(trace.textposition, index);
     return helpers.coerceEnumerated(attributeTextPosition, value);
 }