use logging.SMTPHandler to send email error messages

[jpgard]

• Set up a new data table (secure Google Sheet, as used for MORF authentication) to store users who are permitted to receive email error messages.
• In morf.utils.log, add an SMTPHandler to set_logger_handlers(), if the user is permitted to receive these messages

Log level should be set to error for the email logging.

See https://docs.python.org/3/library/logging.handlers.html#smtphandler and https://gist.github.com/rodvdka/4134185