Adding url helper

Routes can now be named:
$f3->route(['my_route' => 'GET /my/route/@route_id'], function($f3) {
});
The url can be retrieved by name:
[PHP Template]
<?php echo Base::instance()->url('my_route', ['route_id'=>12]); ?>
[F3 Template]
{{ F3::url('my_route', ['route_id'=>12]) }}