Merge remote-tracking branch 'kevin/issue/task-action-button-styling' into features_prs/develop-next

This addresses an issue where the Delete Task Action Button had the wrong
classes which gave it the wrong styling. This corrects the class to make
the Delete button look like the other buttons and still have the red
background on hover.

Merge remote-tracking branch 'kevin/issue/ticket-preview-custom-fields' into features_prs/develop-next

Merge remote-tracking branch 'kevin/issue/disable-canned-responses-on-new-ticket' into features_prs/develop-next

Merge remote-tracking branch 'kevin/issue/local-field-names-in-errors' into features_prs/develop-next

Merge remote-tracking branch 'kevin/issue/private-faq-search-sidebar' into features_prs/develop-next

This addresses issue 4112 where osTicket does not have a default favicon.
This adds favicon images and references to them in the Agent and
Client headers so they appear correctly.

Exclude user lookup done on ticket create from Recent Searches

This addresses an issue where some Vimeo videos are not being sent in
Agent’s responses. This adds `player.vimeo` to the sanitize method’s
iframe section so that the iframe tag is not stripped.

* Export all exportable fields by default - for all queues + adhoc searches
* Export Due Date as well as SLA Due Date

Add ability to add sticky export fields for queues.

* Due date vs. SLA due date
* Misc. datetime fixes

Add ability to edit individual fields without the need to mass-edit all
fields.

Conflicts:
	include/class.thread.php
	include/class.ticket.php

Add support auto email-based auto-referral. This will happen if an email is
sent to multiple departments. For example an email with TO: support &  CC:
billing will result in the ticket getting routed to "support" department and
"billing" getting a referral of the same ticket. This allows both departments
to have visibility of the ticket - which is not possible at the moment.

Move referral checking to thread class