Use KnpMenu to build menu's

Reworked the admin menu's. Now uses KnpMenuBundle to build the full menu. That menu is then used to render the top menu, the tree menu, the breadcrumb and also places the 'page' title in the CMS.

You can add additional top menu items by listening to the following event "kunstmaan_admin.configureMenu". 

To add a listener to you bundle, add the following to your services.yml :

```yaml
    acme_demo.configure_menu_listener:
        class: Acme\DemoBundle\EventListener\ConfigureMenuListener
        tags:
            - { name: 'kernel.event_listener', event: 'kunstmaan_admin.configureMenu', method: 'onMenuConfigure' }
```

When the children are requested from a menu item, the following event is being triggered : kunstmaan_admin.configureMenuChildren

To add a listener to you bundle, add the following to your services.yml :

```yaml
    acme_demo.configure_menu_children_listener:
        class: Acme\DemoBundle\EventListener\ConfigureMenuChildrenListener
        scope: request
        tags:
            - { name: 'kernel.event_listener', event: 'kunstmaan_admin.configureMenuChildren', method: 'onMenuChildrenConfigure' }
```