Limit ticket assignment to department members

Add department setting to limit ticket assignment within department to
department members only. This is necessary for departments with strict
policy on who can access tickets.

The setting doesn't limit team assignment or auto-assignment via help topics
and ticket filters.
Add format param to PersonsName constructor

Accept desired $format as part of class instantiation. System default is
used when none or an invalid format is provided
Extend department membership to groups by default

The setting is useful in making sure the staff members with access to the
department can get alerts and available as possible assignees.
Make department email optional

Departments without email will use the system default email as the default
outgoing email.
Fixes

Add ability to disable canned responses
Fix team drop down selection
Remove priority escalation setting in SLA page (implementation is on todo
        list)
Merge pull request #862 from protich/feature/assign-to-members-only

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