When we remove the client, we should ensure that access_token are also removed.
To ensure that, I created a test that generated an access_token. So when we remove the client, this association should be cascaded and shouldn’t generate an error.
Also I moved some Api related stuff to the ApiBundle (like the developer controler and ClientType form)
Also, retrieve tag from the request instead of the query (which will be the same but it's more easy to test).
Moved down `deleteTagAction` because it conflicted with the new action:
api_delete_tag => /api/tags/{tag}.{_format}
api_delete_tags_label => /api/tags/label.{_format}
And finally, throw exception when a tag is not found before removing it.
