* pkclist.c (do_edit_ownertrust): Different prompt when we're using direct
trust since the meaning is different.
* keyedit.c (trustsig_prompt): Change the strings to match the ones in
pkclist.c:do_edit_ownertrust to make translation easier.
* trustdb.c (trust_model_string, get_validity): Add direct trust model
which applies to the key as a whole and not per-uid.
* options.h, g10.c (parse_trust_model): New. (main): Call it from here to
do string-to-trust-model.