fix: Option defaults were applied as strings... ...not converted to internal representation; add Option methods str2value and value2str for value conversion from and to the strings kept in .ini file; options MAIL_USERNAME, MAIL_TLS_KEYFILE and MAIL_TLS_CERTFILE default to empty strings: NODEFAULT value is a configuration error, and for these options it is ok to keep them unset.

def LOG(*args, **kw):
    pass