eliminating useless salt argument, salt can be generated inside of gnunet-service-set

git-svn-id: https://gnunet.org/svn/gnunet@34431 140774ce-b5e7-0310-ab8b-a85725594a96
-do not run tests if disabled

git-svn-id: https://gnunet.org/svn/gnunet@34432 140774ce-b5e7-0310-ab8b-a85725594a96
rename element's type field to 'element_type'

git-svn-id: https://gnunet.org/svn/gnunet@34433 140774ce-b5e7-0310-ab8b-a85725594a96