adding function to read float from cfg


git-svn-id: https://gnunet.org/svn/gnunet@33273 140774ce-b5e7-0310-ab8b-a85725594a96
read coefficients with cfg functions


git-svn-id: https://gnunet.org/svn/gnunet@33274 140774ce-b5e7-0310-ab8b-a85725594a96