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)
When the association between a tag and an entry is removed, if the tag doesn’t have other entries, we can remove it.
Also add more tests for that part and ensure TagControllerTest is isolated from the rest of the test suite (finally!)
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.
