Search for system emails in To and Delivered-To

Previously, the Delivered-To header was only used if the To header was not
found
Merge pull request #535 from greezybacon/issue/search-to-and-delivered-to

Search for system emails in To and Delivered-To

Reviewed-By: Peter Rotich <peter@osticket.com>
Ignore case for ticket variables on custom fields
Merge pull request #545 from greezybacon/issue/case-ticket-variable

Ignore case for ticket variables on custom fields

Reviewed-By: Peter Rotich <peter@osticket.com>
Allow searching for *any* priority
forms: Add placeholder and promts

Priority field and custom list fields have a prompt value (shows up only for
drop-down widget). And the short and long answer fields have a placeholder
configuration item.
Add placeholder for typeahead lists
staff ticket: Auto select 'Phone' source
staff ticket: Department is optional
staff ticket: Auto select singular help topic

If the system has only one help topic automatically select the help topic
and display any associated custom form.
Merge pull request #547 from greezybacon/issue/search-no-priority

forms: Allow searching any priority

Reviewed-By: Peter Rotich <peter@osticket.com>
Merge pull request #548 from greezybacon/issue/543

Simplify workflow for new ticket by staff

Reviewed-By: Peter Rotich <peter@osticket.com>
smtp: Reuse existing connections where possible

This should speed up the system where several emails and alerts will be sent
through the same SMTP account in the same request.
Add initial concept of a TNEF parser
Inspect file mime type if not provided
tnef: Detect corrupted TNEF streams
Shift error checking into Mail_Parse::parseAddressList
Merge pull request #560 from protich/issue/mailparse

Shift error checking into Mail_Parse::parseAddressList

Reviewed-By: Jared Hancock <jared@osticket.com>
auth: Force session token update on login
Merge pull request #555 from greezybacon/feature/ms-tnef-parser

Parse Microsoft TNEF email attachments

Peter Rotich <peter@osticket.com>