Notify JCommune if its component is being removed

While removal of JCommune component we need to send an HTTP DELETE request to JCommune:
http://{jcommune_url}/wholeforum
Note that if something is wrong while sending of the request, we shouldn't remove anything from database and an appropriate error message should be shown to user.
Also note, that URL for JCommune should be taken from here: POULPE-367 If nothing is set, an error message should appear saying that he has to set respective property in component configuration.