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.

Fixes syntax error introduced with commit 71a6b2a0 & 6e0ddf2e

minor change fix the translation page url

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

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.

Account for agents' name format setting when sorting agents.

MessageThreadEntry::add vs MessageThreadEntry::create

db_real_escape expects a string

Add department relationship to Canned model.

Fix bug brought about by commit #72e9abcf

When issue summary is disabled for a specific help topic, the system uses
help topic name as the subject line.

Due to validation error on disabled subject field the setValue fails to take
in the help topic. The change here allows for forced value set.

Refactor PR #3410 to drop extra commits.
All credit to @jdelhome3578

Remove extra ` ` which throw off the spacing

This fixes sorting and total ticket count.