-move base64 encoder/decoder to util

git-svn-id: https://gnunet.org/svn/gnunet@31156 140774ce-b5e7-0310-ab8b-a85725594a96
-adding CERT record support to dnsparser

git-svn-id: https://gnunet.org/svn/gnunet@31157 140774ce-b5e7-0310-ab8b-a85725594a96
-adding CERT support to DNS plugin

git-svn-id: https://gnunet.org/svn/gnunet@31158 140774ce-b5e7-0310-ab8b-a85725594a96
-note missing features

git-svn-id: https://gnunet.org/svn/gnunet@31159 140774ce-b5e7-0310-ab8b-a85725594a96