Track all certificates that are invalid
Return the valid-from/to as a string instead of an integer

The integer might not fit in all Emacs ints
Display the certificate details when querying
Make all TLS/STARTTLS connections go through the security manager

* net/network-stream.el (network-stream-open-starttls): Use the
network security manager.
(network-stream-open-tls): Ditto.
Make IMAP and POP3 warn unless encrypted, and SMTP warn if passwords

* net/network-stream.el (network-stream-open-starttls): Use the
network security manager.
(network-stream-open-tls): Ditto.

* mail/smtpmail.el (smtpmail-via-smtp): Warn unless encrypted if
we're sending a password.
Doc typo fix
Display the certificate more pretty