Add sendMimeMail() function.

New function sendMimeMail() sends MIMEed mail, text only, or with an
attached file. Existing function sendMailAttachment() modified to make
file attachment optional.
Fix DNS filter failure when requested info type was not present.

DNS filter was failing to return info if the requested info (say 'IP')
was not present in the requested record type. DNS records are "hand
created" and may be in error. Protect ourselves against such errors.
Report by email when scanning overruns the desired time cycle.

Each properties file specifies a desired scanning frequency (e.g. 20
minutes). When this is exceeded, this new code sends an email alert to
administrator urging that the properties file be split into multiple
files.