Fix a few translatable phrase issues

Reviewed-By: Peter Rotich <peter@osticket.com>

mailer: Embed the Message-Id token in @class

Reviewed-By: Peter Rotich <peter@osticket.com>

Ensure consistent name formatting for agents and end users

Reviewed-By: Peter Rotich <peter@osticket.com>

email: Support agents emailing as collaborators

Reviewed-By: Peter Rotich <peter@osticket.com>

Fixes #1854

Several mail clients do not return the Message-ID header in a In-Reply-To or
References header as they should. The assumption by such mail clients is
that the email be threaded based on the Subject header. However, osTicket
does not require the ticket number to be placed in the Subject header and so
has trouble threading email from such systems. osTicket embeds a copy of the
Message-ID header (or compatible version) in the body of the message in
hopes part of the message will be returned.

Many mail clients (such as osTicket) strip and clean the HTML when
processing HTML email. Previously, the message-id token was embedded in a
@data-mid attribute, which was likely stripped before the HTML email would
be returned back to osTicket.

This patch suggests that the token be placed in a @class attribute, which
has a much better chance of returning to osTicket.

Fixes #1926

Also fix bug where bogus charset names like `iso` were confused with valid
charset names starting with that text, such as `iso-8859-2`.

forms: Don't update CDATA when updating old fields

Reviewed-By: Peter Rotich <peter@osticket.com>

Fix several issues with user directory objects

Reviewed-By: Peter Rotich <peter@osticket.com>

mailer: Try harder to find References header

Reviewed-By: Peter Rotich <peter@osticket.com>

filters: Filter user information for email tickets

Reviewed-By: Peter Rotich <peter@osticket.com>

Ensure that the References header that is included with outbound email
definitely includes the References header from an email received into the
system, if at all possible.

When the user is not identified by the web interface, such as processing
email to tickets, attempt to locate and include the user filter information
when matching the filter to the new ticket data.

If an update to an object such as a ticket results in a corresponding update
to the CDATA table, and one or more of the fields have been deleted from the
ticket details form, then, avoid updating the CDATA table for those fields.

This fixes an issue where the CDATA table is dropped and recreated when
fields are added and removed from the form. The table will only contain
fields which are currently on the form when the table is created. Therefore,
deleted fields will never be on the CDATA table and will result in an SQL
error.