Authenticate users using GPG signed emails. automatically set up an anonymous interaction in system doctests. r=stevea
Patches applied:

 * bjorn.tillenius@canonical.com/launchpad--AuthenticateGpgEmails--0--base-0
   tag of rocketfuel@canonical.com/launchpad--devel--0--patch-1588

 * bjorn.tillenius@canonical.com/launchpad--AuthenticateGpgEmails--0--patch-1
   improve login() to make it easier to re-use in order to make a real login

 * bjorn.tillenius@canonical.com/launchpad--AuthenticateGpgEmails--0--patch-2
   setup an anonymous interaction automatically for functional doctests

 * bjorn.tillenius@canonical.com/launchpad--AuthenticateGpgEmails--0--patch-3
   remove login('launchpad.anonymous') from tests, where it isn't needed

 * bjorn.tillenius@canonical.com/launchpad--AuthenticateGpgEmails--0--patch-4
   add SignedMessage which provides easy access to signature and signed content

 * bjorn.tillenius@canonical.com/launchpad--AuthenticateGpgEmails--0--patch-5
   add i and decode to get_signed_payload()

 * bjorn.tillenius@canonical.com/launchpad--AuthenticateGpgEmails--0--patch-6
   fix signed_inline.txt to make tests pass

 * bjorn.tillenius@canonical.com/launchpad--AuthenticateGpgEmails--0--patch-7
   initial hack-up of authenticateEmail, doesn't handle detached signatures yet

 * bjorn.tillenius@canonical.com/launchpad--AuthenticateGpgEmails--0--patch-8
   fix test failure

 * bjorn.tillenius@canonical.com/launchpad--AuthenticateGpgEmails--0--patch-9
   make sure get_signed_payload() returns None if the email isn't signed.

 * bjorn.tillenius@canonical.com/launchpad--AuthenticateGpgEmails--0--patch-10
   forgot to add a file

 * bjorn.tillenius@canonical.com/launchpad--AuthenticateGpgEmails--0--patch-11
   adjust regular expression not to do a greedy match.

 * bjorn.tillenius@canonical.com/launchpad--AuthenticateGpgEmails--0--patch-12
   forgot to add one file....

 * bjorn.tillenius@canonical.com/launchpad--AuthenticateGpgEmails--0--patch-13
   merge rf

 * bjorn.tillenius@canonical.com/launchpad--AuthenticateGpgEmails--0--patch-14
   add gpg keys for sample person and foo bar.

 * bjorn.tillenius@canonical.com/launchpad--AuthenticateGpgEmails--0--patch-15
   use the real gpghandler. various small fixups.

 * bjorn.tillenius@canonical.com/launchpad--AuthenticateGpgEmails--0--patch-16
   use foo bar's and sample person's gpg keys in tests.

 * bjorn.tillenius@canonical.com/launchpad--AuthenticateGpgEmails--0--patch-17
   check that the key used to sign really belongs to the From-user

 * bjorn.tillenius@canonical.com/launchpad--AuthenticateGpgEmails--0--patch-18
   remove MockGpgHandler

 * bjorn.tillenius@canonical.com/launchpad--AuthenticateGpgEmails--0--patch-19
   simply authenticateEmail

 * bjorn.tillenius@canonical.com/launchpad--AuthenticateGpgEmails--0--patch-20
   merge rf

 * bjorn.tillenius@canonical.com/launchpad--AuthenticateGpgEmails--0--patch-21
   remove dependecy on ftests, make authenticateEmail return the authenticated principal.

 * bjorn.tillenius@canonical.com/launchpad--AuthenticateGpgEmails--0--patch-22
   rename login to setupInteraction

 * bjorn.tillenius@canonical.com/launchpad--AuthenticateGpgEmails--0--patch-23
   make ftests.login use setupInteraction to avoid code duplication.

 * bjorn.tillenius@canonical.com/launchpad--AuthenticateGpgEmails--0--patch-24
   clearify documentation

 * bjorn.tillenius@canonical.com/launchpad--AuthenticateGpgEmails--0--patch-25
   remove self from interface.

 * bjorn.tillenius@canonical.com/launchpad--AuthenticateGpgEmails--0--patch-26
   only add the gpgkeys if they're not already in the db

 * bjorn.tillenius@canonical.com/launchpad--AuthenticateGpgEmails--0--patch-27
   merge rf

 * bjorn.tillenius@canonical.com/launchpad--AuthenticateGpgEmails--0--patch-28
   correct typo.

 * bjorn.tillenius@canonical.com/launchpad--AuthenticateGpgEmails--0--patch-29
   create ISignedMessage. clean up SignedMessage.

 * bjorn.tillenius@canonical.com/launchpad--AuthenticateGpgEmails--0--patch-30
   make test_signedmessage.txt documentation instead.

 * bjorn.tillenius@canonical.com/launchpad--AuthenticateGpgEmails--0--patch-31
   merge rf

 * bjorn.tillenius@canonical.com/launchpad--AuthenticateGpgEmails--0--patch-32
   merge rf, resolve conflicts.

 * bjorn.tillenius@canonical.com/launchpad--AuthenticateGpgEmails--0--patch-33
   move login call to test_system_documentation, clear the launchbag on tear down.

 * bjorn.tillenius@canonical.com/launchpad--AuthenticateGpgEmails--0--patch-34
   move setupInteraction to helpers

 * bjorn.tillenius@canonical.com/launchpad--AuthenticateGpgEmails--0--patch-35
   improve regexp matching pgp signatures

 * bjorn.tillenius@canonical.com/launchpad--AuthenticateGpgEmails--0--patch-36
   clean up

 * bjorn.tillenius@canonical.com/launchpad--AuthenticateGpgEmails--0--patch-37
   merge rf

 * bjorn.tillenius@canonical.com/launchpad--AuthenticateGpgEmails--0--patch-38
   remove unnecessary endInteraction

 * bjorn.tillenius@canonical.com/launchpad--AuthenticateGpgEmails--0--patch-39
   merge rf, resolve conflicts.

 * bjorn.tillenius@canonical.com/launchpad--AuthenticateGpgEmails--0--patch-40
   modifications as per reviewer's comments.

 * bjorn.tillenius@canonical.com/launchpad--AuthenticateGpgEmails--0--patch-41
   merge rf

 * bjorn.tillenius@canonical.com/launchpad--AuthenticateGpgEmails--0--patch-42
   fix test failure.