regular GnuPG agent

Both support OpenPGP smartcards and fix claws-mail with gpg have / are problems caused by Seahorse, that are fixed by replacing its agent with the regular GnuPG one and pinentry-gtk2.

Implemented in feature/regular-gnupg-agent.

What would we lose, exactly, by doing that?

Only answer was: nice UI integration.

done in Tails 0.17.

Original created by @tails on 5419 (Redmine)