update nettle to new interface, update deadline scheduler option (doesnt compile without this), update build/install script to use regular nettle and gnutls in ubuntu 16.04 (should also be fine with 14.04 up-to-date), update init_exmimo2 for ubuntu 16.04)

git-svn-id: http://svn.eurecom.fr/openair4G/trunk@7886 818b1a75-f10b-46b9-bf7c-635c3b92a50f