ssl,dtls: move Session Ticket to ssl-utils

Changes:

 - dtls: also support saving session tickets.
 - Drop the length check and let proto_tree_add_item throw exceptions
   on length errors.
 - Use proto_tree_add_item instead of proto_tree_add_uint.
 - Drop "TLS" from header field descriptions, the RFC does not name it
   as such and DTLS can also use it (a draft is in progress that extends
   DTLS with Session Tickets,
   draft-hummen-dtls-extended-session-resumption-01).

Change-Id: I11195217368b7200821d11289b1c5870a1ffe637
Reviewed-on: https://code.wireshark.org/review/3029
Reviewed-by: Evan Huus <eapache@gmail.com>