settings file to turn on/off delete
fixes #2

to fix the database:
drop table audittemp;
create table audittemp like mdl_mail_audit_trail;
insert into audittemp select a.id,a.timesent,a.remote_host,a.touser,a.fromuser,a.subject,a.messagetext,a.attachment_filename,a.attachment_type,a.attachment_data,b.course from mdl_mail_audit_trail as a,mdl_mail_privmsgs as b where b.folder=0 and a.timesent=b.timesent and a.subject=b.subject group by a.id;

delete mdl_mail_audit_trail;
insert into mdl_mail_audit_trail select * from audittemp;