Changes

library/gsup: rework f_gen_{tr,ts}_ss_ies() and SS templates

* Add missing param restrictions to SS related templates.
* f_gen_{tr,ts}_ss_ies(): proper template param restrictions.
* f_gen_ts_ss_ies(): return a template, not a value.
* f_gen_ts_ss_ies(): append IEs using list index.
* f_gen_ts_ss_ies(): isvalue() -> istemplatekind()
                     to allow passing template lists.
* f_gen_tr_ss_ies(): istemplatekind() -> ispresent()
                     to allow passing template lists.
* f_gen_tr_ss_ies(): 'omit' -> '*' for optional params.

Change-Id: Ia611ffa3845d48c5553c70f10981aa029d00d873