This addresses a vulnerability where there was no `X-Frame-Options` header
which could potentially allow click jacking. This adds the
`X-Frame-Options: SAMEORIGIN` header so it will remove any chance of click
jacking. According to Mozilla Developer Docs:
```
SAMEORIGIN
The page can only be displayed in a frame on the same origin as the page
itself.
```

* 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.

Update three phrases with from "Internal error" to "Internal error occurred" since it's the most common phrase

Missing ":" and h2 / h3 was mixed at "Prerequisites", I guess it shall be h3 here

This pass also makes a stride at adding correct punctuation and making error
phrases consistent.

This is my attempt at removing similar texts from the translator work load.
It also makes an attempt at dropping some misspelled words and works toward
standardizing some phrases.

Previously, the create method was used to create a new instance of an orm
model (which would later result in an INSERT when persisted); however, some
classes require or utilize varying parameters to their create() method,
which PHP7 considers an error. Methods in subclasses must be defined with a
calling signature compatible with the parent class.

This patch shifts the concept of model creation to the constructor. Now, the
constructor of ORM models is required to be compatible with that of
ModelBase class. Now that most models do not define a constructor, this is
much easier to control, and much more logical.

Also, remove an issue where assignments on a relationship field to an
instance of a super class of the foreign model would raise an error. This
was previously addressed by re-classing the instance in the
ModelInstanceManager::getOrBuild(); however that design would create
multiple instances of the same object in memory, which defeats one of the
primary design concepts of the ORM. This patch addresses the issue by
allowing super-classes of the declared foreign model in relationship
assignments.

This commit attempts to remove all coding standard warnings emitted by PHP
7.0.

This fixes a regression in the option parsing where --setup would be
interpreted as --setup -e -t -u -p

Also, some parts of osTicket, like internationalization and plugins need
read access to a directory in order to get a list of installed plugins and
language packs.

(rather than deleted after install)

This allows the MANIFEST to be hidden from HTTP requests since the entire
include/ folder is already denied for Apache.

As an option, this will allow preventing deployment of files not tracked
with git. It's also about twice as fast as the PHP version.

This allows files which are edited on the fly during deployment to be
tracked so that they are not unnecessarily deployed again in the next
deployment run. It also allows for more creative deployment strategies using
something like `git ls-files -s`

This is required with the connection to Dept::getEmail()->send(...)

This patch (which needs further development), introduces an extra field to
the %attachment table to store a file's name, in the event that two files
with the same content are stored in the database with differing names. In
such a case, the name is stored in the %attachment table. This allows the
attachment to specify a different name each time the same file is attached
to something in the system.