peerstore: doxygen


git-svn-id: https://gnunet.org/svn/gnunet@34038 140774ce-b5e7-0310-ab8b-a85725594a96
fixing documentation


git-svn-id: https://gnunet.org/svn/gnunet@34039 140774ce-b5e7-0310-ab8b-a85725594a96