Export node addresses in plain text instead of raw bytes

This PR modifies the output format for node addresses. Instead of exporting raw bytes, we encode them into human readable string.

Maybe this should be a feature toggled by an option flag.

Example output with graphml

    <node id="0213351211aecfd9688a1b5205d0949857f9349e4128b9f7dd8adf3c699207e494">
      <data key="d0">0213351211aecfd9688a1b5205d0949857f9349e4128b9f7dd8adf3c699207e494</data>
      <data key="d1">1524429955</data>
      <data key="d2" />
      <data key="d3">1551b2</data>
      <data key="d4">Murray Rothbard</data>
      <data key="d5">ipv4://46.101.51.48:9735</data>
      <data key="d6">0</data>
      <data key="d7">1</data>
    </node>
    <node id="027ccec61f4bf1fafb5156931da6527dc104ec3613dd4f4050161d89dd76ab494c">
      <data key="d0">027ccec61f4bf1fafb5156931da6527dc104ec3613dd4f4050161d89dd76ab494c</data>
      <data key="d1">1526724629</data>
      <data key="d2" />
      <data key="d3">ff5050</data>
      <data key="d4">heliacal</data>
      <data key="d5">ipv6://2001:470:5f:5f::232:9735</data>
      <data key="d6">0</data>
      <data key="d7">1</data>
    </node>
    <node id="02b66f6950d58aa6986ea50114d79d5ec798ed6c628964914d4e37f2abbeed0082">
      <data key="d0">02b66f6950d58aa6986ea50114d79d5ec798ed6c628964914d4e37f2abbeed0082</data>
      <data key="d1">1583584341</data>
      <data key="d2" />
      <data key="d3">68f442</data>
      <data key="d4">SPQR</data>
      <data key="d5">torv2://dhwxl6ozvsiat4zq:9735</data>
      <data key="d6">0</data>
      <data key="d7">1</data>
    </node>
    <node id="030bfda7ea0c5a6ebfc941e0ed34d7b2306000838d922877a4b8b1f21cb6dc3cc7">
      <data key="d0">030bfda7ea0c5a6ebfc941e0ed34d7b2306000838d922877a4b8b1f21cb6dc3cc7</data>
      <data key="d1">1585958513</data>
      <data key="d2">2200</data>
      <data key="d3">3399ff</data>
      <data key="d4">Oldschool</data>
      <data key="d5">torv3://itqwxmv5wi3w3szyfhgyufooykdvic5ehe45crdpw6d6ortdmcvzqfad:9735</data>
      <data key="d6">0</data>
      <data key="d7">3</data>
    </node>

lnresearch / topology

Export node addresses in plain text instead of raw bytes #14