Add Agents and Users setting pages
Move global settings to System settings

The setting is no longer ticket thread specific. Disabling html is now
system wide setting for disable-able textarea widgets as well as email
correspondence.

Settings for storage backend and general max size setting for agents

Fixes #1809

Refactor filter.yaml and related code base
Move isBanned routine to banlist class and make it banlist specific
Refactor how canned responses get list of filters

Fixes https://github.com/osTicket/osTicket-1.8/issues/1673

Add ability to add tasks to tickets.

Introduce the concept of tasks. Tasks are to do list that can be attached to
any object e.g Ticket.

Conflicts:

	include/i18n/en_US/form.yaml
	include/staff/templates/dynamic-field-config.tmpl.php
	include/staff/ticket-view.inc.php
	include/staff/tickets.inc.php
	scp/js/scp.js

oops: Fix crash upgrading to c7c82835

oops: Fix crash rendering ticket view

oops: Fix crash posting response to ticket

oops: Fix refresh url after ticket reply post

orm: Locate annotations after the root model's fields

orm: Add PK field check for DISTINCT aggregate expressions

When using the DISTINCT option for aggregate expressions, ensure that when a
relationship is used in the aggregate, that a single field of the remote
model's primary key is used — rather than the foreign key, since it would
never have more than one unique value.

search: Re-implement basic ticket search

oops: Couple trivial changes

oops: Fix date formatting for PDF output

oops: Fix staff profile view and update

oops: Fix canned response listing

orm: Fix crash compiling WHERE IN (nested select)

nav: Move settings/email to email/settings

i18n: Make field visibility config translatable

oops: Fix crash adding field to custom form

forms: Fix `required` flag transfer to FormField

oops: Fix bad merge on new ticket by staff

forms: Show uneditable fields on new ticket by staff

oops: Fix bad merge on client ticket view

Introduce the concept of role-based access for agents.

The commit also renames some fields in department table.

Allow fields to be configured for view / edit / required for both agents and
end users. Fields can also be disabled now so that the field remains in the
form but is no longer displayed for new entries.

Allow tickets to be created without a subject — use the help topic full name
instead.

This is necessary so we can consolidate various settings and permissions
into one bit mask field.

Determine and set a reasonable max file size on install
Remove file extension restrictions - transition to mime types

This patch also makes a slight edit to mPDF to allow better detection of
substitions in characters, as the DejaVu fonts shipped do not support Thai
glyphs.