Method remove

@param owner @param sharingKey @param mapKey @return hash(sharingKey.metadata) | the new root hash of the tree @throws IOException

(WriterData base,
                                         PublicKeyHash owner,
                                         SigningPrivateKeyAndPublicHash sharingKey,
                                         byte[] mapKey,
                                         MaybeMultihash existing,
                                         TransactionId tid)