Added details about Lifecycle Hooks (#1664)

* Added details about Lifecycle Hooks

Mostly a clarification for beginners without prior knowledge about what Lifecycle hooks are. Makes it easier to understand when perhaps only knowing that the developer has a `mounted()` hook. 

I left out the function syntax because of generality. Add if it makes more sense to add. I am not fully knowledgable in Vue yet.

* add (de)activated to lifecycle hooks list in style guide

Author: Knogobert

src/v2/style-guide/index.md

@@ -1514,6 +1514,16 @@ This is the default order we recommend for component options. They're split into
 9. **Events** (callbacks triggered by reactive events)
   - `watch`
   - Lifecycle Events (in the order they are called)
+    - `beforeCreate`
+    - `created`
+    - `beforeMount`
+    - `mounted`
+    - `beforeUpdate`
+    - `updated`
+    - `activated`
+    - `deactivated`
+    - `beforeDestroy`
+    - `destroyed`
 
 10. **Non-Reactive Properties** (instance properties independent of the reactivity system)
   - `methods`