[geary] (18 commits) ...Merge branch 'wip/20-cert-pinning' into 'master'

[Michael Gratton <mjog src gnome org>]

Summary of changes:

  3c89a2f... Update Geary.ConnectivityManager to check a GSocketConnecta (*)
  19d2fdf... Update Geary.Endpoint API and source (*)
  3f04e5e... Tidy up all of the various untrusted_host signals (*)
  e94e466... Remove now-unsed validation code from Geary.Engine (*)
  884500a... Add Geary.ProblemType for TLS cert validation errors, clari (*)
  67ec69a... Modernise cert prompting impl to work with new account stat (*)
  82c972f... Replace controller's GCR pinning impl with new CertificateM (*)
  0d93696... Don't update status for IMAP connection problems multiple t (*)
  1fa342c... Remove now unsed Endpoint.trust_untrusted_host prop and rel (*)
  c0b5d44... Don't block handling GTlsConnection::accept-certificate (*)
  2e344d7... Handle untrusted certs when adding a new account (*)
  1a2bb28... Handle untrusted certs when adding a editing account server (*)
  97971ce... Don't prompt for untrusted host as validation when account  (*)
  cda0e7f... Simplify CertificateManager's db pinned cert management (*)
  9ade041... Implement loading and saving certs in CertificateManager (*)
  812bce2... Fix brown-paper-bag file name typo (*)
  6b9ae90... Re-enable GCR support for cert pinning (*)
  da2d676... Merge branch 'wip/20-cert-pinning' into 'master'

(*) This commit already existed in another branch; no separate mail sent