Added a special onDeconstruct template function that allows a function to be invoked when the element is being destroyed.

ignite-template.js

@@ -775,6 +775,25 @@ class IgniteTemplate {
         return this;
     }
 
+    /**
+     * Adds an event handler that gets called when this element is being deconstructed from the DOM.
+     * @param {Function} eventCallback The callback function to be invoked once this element is disconnected.
+     * @returns {IgniteTemplate} This ignite template so function calls can be chained. 
+     */
+    onDeconstruct(eventCallback) {
+        if (eventCallback) {
+            this._destructors.push(() => {
+                IgniteRendering.push();
+
+                eventCallback();
+
+                IgniteRendering.pop();
+            });
+        }
+
+        return this;
+    }
+
     /**
      * Adds a CSS property to this template with a value and priority.
      * @param {String} name The name of the CSS property to set.