- populate underlay db 


git-svn-id: https://gnunet.org/svn/gnunet@31815 140774ce-b5e7-0310-ab8b-a85725594a96
- use asynchronous to speedup sqlite db writes


git-svn-id: https://gnunet.org/svn/gnunet@31816 140774ce-b5e7-0310-ab8b-a85725594a96