[fix] tmail_gpg: remove final CRLF added to respect OpenPGP convention
[fix] let's be clear when a key if not found
[fix] check for MIME boundaries better
[fix] raise an error when trying to sign a not properly encoded content
[fix] ensure RFC3156 content is calculated with raw content when checking a signature (without TMail content reorganization) and using the TMail generated content when creating a new mail
[fix] ensure to_rfc3156() is strict, and ensure quoted_body message is properly added for signed/crypted
[licence] updated copyright years and added missing headers
[fix] updated the TMail extension
[evol] added changes requested by upstream author to be included in TMail 1.3
[fix] the tmail gpgme addon was unquoting the body content by mistake
[evol] add missing licensing terms
[evol] check content-type protocol parameter when validating pgp mail content, and renamed tmail_extra library into tmail_gpg (as it is dedicated to gpg mails only)