Stabilize v1.10 release

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

Disable sorting on ThreadEntry::email_info__mid lookups for email processing
which results in an on-disk temporary table.

Load and cache all the attachments on a thread prior to rendering the items.
That removes the need to run a query per thread item to check for- and fetch
attachments.

This patch changes the automatic GROUP BY clause for annotations in the ORM
including aggregate queries (like COUNT), by allowing the query to specify
"distinct" fields. If distinct fields are specified, then no other fields
are automatically added to the GROUP BY clause of the compiled query.

This will likely only be supported by MySQL, as other engines and the ANSI
standard require all non-aggregate fields in the SELECT clause to be present
in the GROUP BY clause.

If the configuration for the file backend is set to something invalid, do a
better job of falling back to database-backed attachments.

i18n: Use horizontal, alt tabs for translatable content tabs

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

orgs: Add ticket sharing feature

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

This feature allows (by option) an organization to allow its members to see
tickets from other members. It can be used beside or instead of the
automated collaboration feature. Now, collaborators retain access to tickets
on which they participate; however, sharing can be used to enable access to
other tickets owned by their organization.

Conflicts:
	WHATSNEW.md
	include/class.ticket.php
	include/class.topic.php
	include/staff/faq-view.inc.php
	include/staff/helptopics.inc.php

Fix for issue #2557 

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

Fix issues deploying with PHP 5.6

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

db: Forbid static zones like 'CDT'

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

Send header information before output. Fixes #2554

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

lock: Fix lock timing if php and db use different time zones

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

Blank page from 'register' link in notification email to guest user.

Reviewed-By: Jared Hancock <jared@osticket.com>

Fix posting-user determination in Thread::postEmail

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

reduce memory usage when storing file in DB

Reviewed-By: Jared Hancock <jared@osticket.com>

include @greezybacon suggestion on fix

Fixes #2350 in `develop`