Add init events for components

An event, ``'ons-component:init'``, will be fired when a component is initialized.
A help function, ``ons.eventToComponent(event)``, can be used to extract the component from the event object.

e.g.
```javascript
document.addEventHandler('ons-navigator:init', function(e) {
  var navigator = ons.eventToComponent(e);
  navigator.pushPage('some_page.html');
});
```
In this time, ons-page may not be attached on DOM tree.
Fire init event at the same timing with fireActualPageInitEvent().
See details: https://github.com/argelius/OnsenUI/blob/master/framework/directives/page.js#L74