And remove unsupported filter of email headers

But don't send out canned responses for new tickets that matched a filter
with an attached canned response if that response is not enabled. Also,
explicitly block deletes to filters that are in use.

- Move access to it's own table.
- Refactor what department membership means in relation to group access

when they are in use by email filters

Add print options supports - staff can now print a ticket thread without internal notes + select paper size on the fly

Add Team::hasMember utility method to assist in determining if a ticket is
owned by a team that he currently-logged-in-staff is a member of. Then,
check if the ticket is assigned to a staff member other than the current
staff or to a team that the current staff is not a member of. If so (the
ticket is not assigned to the current staff), then display the warning
banner showing who currently owns the ticket.

Protect againts cross-site request forgery attacks by requiring a special
form-field or header to be sent with requests that modify ticket system
data.

This meant a slight change to the AJAX ticket locking mechanism. It was
defined to lock with a GET request; however, GET requests are defined as
safe methods and should not modify backend data (such as a lock
acquisition). Therefore, the the lock acquire AJAX method was changed to
require a POST method.

Also remove old, no-longer-used staff panel include files

Rather than defaulting to either showing answered tickets or closed tickets
if there are no open tickets.

Allow staff members the ability to select a default paper size which will be
used in printing tickets via PDF. In the future, this may be overridden per
ticket by a dialog box at print time.