Encode html entities of cached form data

This commit addresses an SQL injection vulnerability in ORM lookup
function.

* ORM implementation failed to properly quote fields, used in SQL
statements, that might originate from unsanitized user input.

* AttachmentFile lookup allowed for key based SQL injection by blindly
delegating non-string lookup to ORM.

This addresses issue where upon deletion of a form field and all its
entry values, the field record wouldn't be deleted from the `form_field`
table. This links another issue where you can't delete a list if its
been a field before. This is due to the list delete() function that
checks for list field records in the `form_field` table.

This is necessary to force a particular timezone on a DateTimeField entry.
If timezone is not set then user's timezone is assumed.

Address edge cases where timezone mixups happens on DateTimeField

Allow datetime field to be timezone agnostic (not timezone aware) to display
the timezone used to set the field. The timezone of the last user or agent
that edited the field is used.

This fixes an InconsistentModelException error when editing thread
entries with inline images. The fix assumes that inline images are
re-attached when a new ThreadEntry is created and the body is copied
from the previous entry. Only the non-inline attachments need to be
moved in the update query.

This addresses issues #1964 & #3668 where $cfg might be null and cause a
non-object error. Check if $cfg is set, if not return the default
en_US language.

Fixes syntax error introduced with commit 71a6b2a0 & 6e0ddf2e

minor change fix the translation page url

Changes 'Permisions' to the correct spelling 'Permissions'.

Move orphaned tasks on department deletion to the default department

Display Loading Overlay when posting a response or a note to a ticket.

Can not update list item abbreviation because update() method is
expecting 'abbrev' key so this corrects the key.

* HTTP Option: TRUSTED_PROXIES (default: <none>
To support running osTicket installation on a web servers that sit behind a
load balancer, HTTP cache, or other intermediary (reverse) proxy; it's
necessary to define trusted proxies to protect against forged http headers.

* HTTP Option: LOCAL_NETWORKS (default: 127.0.0.0/24)
When running osTicket as part of a cluster it might become necessary to
white list local/virtual networks that can bypass some authentication
checks.

* Validate CLIENT_IP to make sure it's a valid IP address.

Encode html chars on helpdesk title

Defer to agent's timezone on due date `datetime` selection instead of
defaulting to GMT.

Fix case where filter applying 'Use Reply-To Email' filter action
triggers a reprocessing loop that exhausts php memory.

Fixes missing due date on task create caused by invalid datetime format sent to db.

Use class instead of id on form element that triggers overlay on submit.

Address cases where incoming email doesn't have message-id or references

Allow closed thread to be reopened when when is passive mode

Add support for threading email conversations happening outside the system.
Autoresponders are paused when threading is on passive mode. Alerts may
still go out to agents as configured.