[PropelParamConverter] add exclude option for Pk and fields, with tests a

[jaugustin]

hi,

This add an exclude option that could be use to exclude request attributes from being use by the converter

If you have a route like /my-route/{slug}/{name}/edit/{id}
You can exclude "name" and "slug" by setting the option "exclude" :

<?php

/**
 * @ParamConverter("post", class="BlogBundle\Model\Post", options={"exclude"={"name", "slug"}})
 */
public function myAction(Post $post)
{
}