This patch affords an administrator the ability to remove the
[#%{ticket.number}] from the email template subject line for the new ticket
autoresponse and the new message autoresponse. Previously, the ticket number
with a prefixed hash in brackets was used to identify which ticket thread an
email was in reference to.

With this patch, the email message-id (which was already kept on file) is
sent in the MIME "References" header. When a user responds to and
autoresponse email, the "References" will include this message-id in the
return email. The ticket thread is then matched up with the email based on
the message-id rather than the subject line.

Ticket numbers are still supported in the subject line, in the event that
non-compliant email clients do not properly include the References header.

Previously, the @ext attribute for the phone number field was assumed to be
included. An XML payload without the @ext attribute would have been
corrupted to include only the first digit of the phone number, which would
fail validation.

This patch correctly handles the XML payload without the @ext attribute for
the phone number. Subsequently, the <phone_ext> element is now also valid
(and optional as well).

Fixes #670

Incoming messages with empty body and an inline attachment might not have
parts - depending on encoding used.

* Use "-" tag for emails with empty body/message

Change /api/task/* -> /api/tasks/*

Remove piping setting option - it's now part of ticket create service (which include XML & JSON)

Implement remote cron as api task (more to come)

Log ALL API errors along with API Key used

    * Don't require a content-type, so data:,this is content
      is perfectly allowable. Such content is assumed text/plain
    * Support the charset hint, so
      data:text/plain;charset=iso-8859-1,content here
      will be translated to UTF-8 if the php iconv() function exists.
      Otherwise, content is left intact and assumed by the database to by
      UTF-8 already