Make all descriptor instances serializable.

package org.torproject.descriptor;

import java.io.Serializable;

import java.time.Duration;

import java.time.LocalDateTime;

import java.util.List;

   */

  List<RelayLine> relayLines();

  interface RelayLine {

  interface RelayLine extends Serializable {

    /**

     * Fingerprint for the relay's RSA identity key.

package org.torproject.descriptor;

import java.io.Serializable;

import java.util.SortedMap;

/**

 *

 * @since 1.0.0

 */

public interface BandwidthHistory {

public interface BandwidthHistory extends Serializable {

  /**

   * Return the original bandwidth history line as contained in the

package org.torproject.descriptor;

import java.io.File;

import java.io.Serializable;

import java.util.List;

/**

 *

 * @since 1.0.0

 */

public interface Descriptor {

public interface Descriptor extends Serializable {

  /**

   * Return the raw descriptor bytes.

package org.torproject.descriptor;

import java.io.Serializable;

/**

 * Contains details about an authority and its vote that contributed to a

 * consensus.

 *

 * @since 1.0.0

 */

public interface DirSourceEntry {

public interface DirSourceEntry extends Serializable {

  /**

   * Return the raw directory source entry bytes.

package org.torproject.descriptor;

import java.io.Serializable;

/**

 * Contains the signature of a network status consensus or vote.

 *

 *

 * @since 1.0.0

 */

public interface DirectorySignature {

public interface DirectorySignature extends Serializable {

  /**

   * Return the digest algorithm, which is "sha1" by default and which