-doxygen improvements

git-svn-id: https://gnunet.org/svn/gnunet@32902 140774ce-b5e7-0310-ab8b-a85725594a96
fixng crash on shutdown


git-svn-id: https://gnunet.org/svn/gnunet@32903 140774ce-b5e7-0310-ab8b-a85725594a96
Add gnunet-nse program to show network size estimates.


git-svn-id: https://gnunet.org/svn/gnunet@32904 140774ce-b5e7-0310-ab8b-a85725594a96