3508 whitelist Soundcloud and 3509 unwhitelist 4shared

Whitelist Soundcloud http://code.google.com/p/otwarchive/issues/detail?id=3508

Remove 4shared from whitelist http://code.google.com/p/otwarchive/issues/detail?id=3509

Note that this only whitelists HTML5 embeds from Soundcloud. Flash embeds from that site use allowscriptaccess, which we do not allow.