Allow the installation to use the same streams config and schema signatures
as the migrater

Allow the install to install mulitple database streams

Allow `streams.cfg` to be implied as 'core', which will default to only
upgrading the core osTicket stream.

Use signature to describe snapshots rather than md5

This patch allows the upgrader to upgrade multiple database update
'streams'. The main stream is renamed to 'core' to reflect changes made
to the config class. This will significantly ease customizations
requiring database customizations, and will make plugins requiring
database changes possible.

Add customer-facing pages and federated email templates

Reviewed-By: Jared Hancock <jared@osticket.com>

 - Supported pages: landing, offline, thank-you and other

Provide failsafe encoding for email message bodies
Reviewed-By: Peter Rotich <peter@osticket.com>

If the body of an email message is written and encoded with an unrecognized
charset (like 'iso', for instance), then use the original text, assumed to
be 8-bit encoded. This patch will create idiosyncrasies, where text might be
transcoded to utf-8 incorrectly, but it should eliminate instances where
email message bodies are missing due to incorrect charset labels.

Fix pass-by-reference bug in authentication signal

Disable cron during upgrade

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

Turn off output_compression for downloads

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

Send the object context, as documented

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

Looks like a long standing, yet-to-be-fixed PHP bug, where
zlib.output_compression can result in the output buffer not completely being
flushed. This is especially critical for downloads where the tail of the
file might be lost.

https://bugs.php.net/bug.php?id=19436

Prefer session persistent configuration over database

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

Make the Unpacker arguments extensible
Reviewed-By: Peter Rotich <peter@osticket.com>

This will allow setting something in the session and having that value
override the value from the database. If ->persist() is called for a given
key, a following ->get() will result in the session persisted value being
returned. ->set() will still save the value in the database.

This is mostly useful for last-mile scenarios (and future plugins) that need
to affect the configuration of the system without altering the data in the
configuration table.

Turns out that the $args passed into the run() method of the Unpacker are
not correctly utilized and so, it is not correctly extensible

Add deploy cli script

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

Install may fail on Windows platforms

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

Fix printing / attachment download issues

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

Implement a simple signal (event) architecture

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

This allows another signal condition to the connection, so that, in addition
to the (sub) class, another check can be made before the signal is delivered
to the connected callable

This will allow folks following the git development model to checkout the
sourcecode to one folder, follow an upstream git brach, and deploy the
osticket installation from a current branch to a location somewhere.

The deploy process differs from the unpack process in that it does not
assume to be inside an 'upload/' folder from the install zipball, and it
does not deploy the 'setup/' folder.

The include folder is still supported to be installed elsewhere.

- Force destination folder to always have a trailing slash
- Log if verbosity is set to stdout
- Use MD5 to see if copy is necessary

Inside cli modules, use internal stdout and stderr objects rather than
writing directly to the PHP outputs. This will allow for significantly
easier regression testing integration.