Add some examples for onCreated and onDestroyed

docs/client/full-api/api/templates.md

@@ -120,6 +120,16 @@ These callbacks fire once and are the first group of callbacks to fire.
 Handling the `created` event is a useful way to set up values on template
 instance that are read from template helpers using `Template.instance()`.
 
+```javascript
+Template.myPictures.onCreated(function () {
+  // set up local reactive variables
+  this.dataVar = new ReactiveVar("some value");
+
+  // register this template within some central store
+  GalleryTemplates.push(this);
+});
+```
+
 {{> autoApiBox "Template#onDestroyed"}}
 
 These callbacks are called when an occurrence of a template is taken off
@@ -131,6 +141,15 @@ This group of callbacks is most useful for cleaning up or undoing any external
 effects of `created` or `rendered` groups. This group fires once and is the last
 callback to fire.
 
+```javascript
+Template.myPictures.onDestroyed(function () {
+  // deregister from some central store
+  var positionInStore = GalleryTemplates.indexOf(this);
+  if (positionInStore !== -1)
+    GalleryTemplates.splice(positionInStore, 1);
+});
+```
+
 
 <h2 id="template_inst"><span>Template instances</span></h2>