Milestone 2 reached

Oops, I skipped announcing that milestone 1 was reached in December...

Husk can encrypt passing mails for simple cases, meaning:

• for all recipients of an email, a valid certificate is locally available.
• if that is not the case, Husk will not modify the email.
• Husk will not query keyservers (or other sources) for certificates - this is part of milestone 3.