Change collation to utf8_general_ci

This is necessary to avoid illegal mix of collations error during upgrade
for MySQL with strict language setting.
i18n: Allow Unicode characters in the username
oops: Allow digits in usernames
mysqli: Numbers with leading zeros are strings
Allow manager to be set even when a department has no members

This is necessary to allow for creative department based access control and
alerts.
Support viewing tickets without a departments

This can happen when associated department is private and the system has no
default department (which is possible with v1.6 upgrade)
sla: New SLA's default to alert when overdue
faq: Fix last modified time not to be midnight

It was also the last-modified date of the category -- not the actual FAQ
article itself

NOTE: For osTicket-1.7, the time portion is not shown because it is not
available in the database.
Close tip popup on click outside the tip box.

Credit: http://stackoverflow.com/a/7385673/2867073
fix: Restrict access to closed tickets

When checking ticket access - only consider assignment IF the ticket is
open. This is required since staff_id field is overloaded to show who closed
the ticket.
Restrict access to closed tickets based on staff's access control.

Background: osTicket allows access to assigned open tickets (both personal
and team assignments) regardless of the assigned department or group. This
is necessary to allow staff to work on tickets in an otherwise restricted
department.

When a staff member closes a ticket, they're credited (ticket.staff_id is
set to staff's id) for the purpose of showing who closed the ticket.
osTicket mistakenly allowed continued access to closed tickets even when the
staff doesn't have access to the ticket based on departmental access.