Add May First/People Link CA to /usr/local/share/ca-certificates

This is so that we can use the zimmermann.mayfirst.org keyserver over
HKPS.

See:

  https://support.mayfirst.org/wiki/faq/security/mfpl-certificate-authority
  https://en.wikipedia.org/wiki/Key_server_%28cryptographic%29#Keyserver_examples
  https://trac.torproject.org/projects/tor/wiki/doc/TorifyHOWTO/GnuPG#ListofOpenPGPX.509KeyserverorPoolKeyservers
  https://we.riseup.net/riseuplabs+paow/openpgp-best-practices#consider-making-your-default-keyserver-use-a-keyse
Added a PGP related TODO
Added PGP keys for dkg & jamie

This is so that we can verify the May First/People Link CA with PGP.

See:
https://support.mayfirst.org/wiki/faq/security/mfpl-certificate-authority#Verifyingthecertificate