arrange sample plugins by SMTP phase
arrange sample plugins by SMTP phase

and add comments to that effect, provides the uninitiated with clues
about which data each plugin actions upon

salvis/qpsmtpd,salvis/qpsmtpd,msimerson/qpsmtpd,sieutruc/qpsmtpd,smtpd/qpsmtpd,sentinelleader/qpsmtpd-dev,smtpd/qpsmtpd,priyadi/qpsmtpd,priyadi/qpsmtpd,sentinelleader/qpsmtpd-dev,msimerson/qpsmtpd,sieutruc/qpsmtpd,priyadi/qpsmtpd,sieutruc/qpsmtpd