[Indicators] Add notion of indicators

Add indicators as a category-of-extension, utilized
from the bottom bar to populate its contents.
WTD-608.

platform/commonUI/general/src/BottomBarController.js

@@ -0,0 +1,36 @@
+/*global define*/
+
+define(
+    [],
+    function () {
+        "use strict";
+
+        /**
+         * Controller for the bottombar template. Exposes
+         * available indicators (of extension category "indicators")
+         * @constructor
+         */
+        function BottomBarController(indicators) {
+            // Utility function used to instantiate indicators
+            // from their injected constructors.
+            function instantiate(Indicator) {
+                return new Indicator();
+            }
+
+            indicators = indicators.map(instantiate);
+
+            return {
+                /**
+                 * Get all indicators to display.
+                 * @returns {Indicator[]} all indicators
+                 *          to display in the bottom bar.
+                 */
+                getIndicators: function () {
+                    return indicators;
+                }
+            };
+        }
+
+        return BottomBarController;
+    }
+);