client manager: documentation

git-svn-id: https://gnunet.org/svn/gnunet@34087 140774ce-b5e7-0310-ab8b-a85725594a96
psyc, psycstore: retrieve state and history

git-svn-id: https://gnunet.org/svn/gnunet@34088 140774ce-b5e7-0310-ab8b-a85725594a96