Load controllers with FQCN.

Fixes part of #571 

It's BC and works by the following syntax:

```php
Route::set('default', 'controller-name/<action>')
	->defaults(array(
		'controller' => '\Acme\Module\Controller\Demo'
	));
```

The <controller> syntax won't work but I think that when using FQCN you should not use variable controller parameters.

@acoulton or @enov can you please review if this is okay?