fix a -Wformat
move aghermann globals from common/ into aghermann/

those are gsl_rng *rng; and int num_procs;
aghermann -n EXPDIR for headless mode

Only init a CExpDesign in that dir, do nothing else, the idea being to
run it under valgrind.
forgot to give metrics::swu::SPPack some defaults

also, move some simple methods to headers
replace ASPRINTF macro with a proper string agh::str::sasprintf()

DEF_UNIQUE_CHARP found leaking, oh dear.
make aghui::pop_question take same args as pop_ok_question, touch up strings