[Scrolling] Add JSDoc, clean up

Clean up scripts for Scrolling List view and add
some JSDoc. WTD-534.

platform/features/scrolling/src/RangeColumn.js

@@ -9,19 +9,31 @@ define(
         "use strict";
 
         /**
+         * A column which will report telemetry range values
+         * (typically, measurements.) Used by the ScrollingListController.
          *
          * @constructor
+         * @param rangeMetadata an object with the machine- and human-
+         *        readable names for this range (in `key` and `name`
+         *        fields, respectively.)
          */
         function RangeColumn(rangeMetadata) {
             return {
+                /**
+                 * Get the title to display in this column's header.
+                 * @returns {string} the title to display
+                 */
                 getTitle: function () {
                     return rangeMetadata.name;
                 },
+                /**
+                 * Get the text to display inside a row under this
+                 * column.
+                 * @returns {string} the text to display
+                 */
                 getValue: function (domainObject, data, index) {
-                    return data.getRangeValue(
-                        index,
-                        rangeMetadata.key
-                    );
+                    var value = data.getRangeValue(index, rangeMetadata.key);
+                    return value && value.toFixed(3);
                 }
             };
         }