Introduce ability to create sub-categories to knowledge base categories

Syntax Errors Hotfix

Fixes syntax error introduced with commit 71a6b2a0 & 6e0ddf2e

Typo error missing a parenteses

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

i18n v1.10 translation issues

Fixes issue #3620. is_numeric changed in 7.0.0 causing causing the contact form and sometimes login to break. is_string works on any version. The upstream Spyc now uses regex to verify instead of is_numeric, in a way similar to this commit. Waiting on upstream to merge other customizations we've made.

Thanks @rayfoss  

Now sold exclusively without Crowdin commits.

issue template

List Item Abbreviation

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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

Ticket Filter Memory Leak

Task Duedate Timezone 

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.

upgrader: Fix undefined function

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upgrader: Fix crash on SequenceLoader

Reviewed-By: Peter Rotich <peter@osticket.com>

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.

This checks to make sure string translation function '__()' is defined.

Passive Threading Revisited

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

thread: Fix crash processing problem attachments

Cleanup Client Ticket Table

1.10 :: Fix Last Updated variable for Help Topics

Passive Email Threading