Remove Application Development page

The Application Development page is thin on content and mainly covers
required knowledge for development using the deprecated Canterbury era
applications.

This is superfluous, remove it.

Signed-off-by: Martyn Welch <martyn.welch@collabora.com>

content/developer/app-dev.md

-+++
-short-description = "A step by step guide for developing your first Apertis application"
-license = "CC-BY-SAv4.0"
-title = "Application Development"
-weight = 100
-aliases = [ "/old-developer/latest/app-dev.html", "/old-developer/v2019/app-dev.html", "/old-developer/v2020/app-dev.html", "/old-developer/v2021pre/app-dev.html", "/old-developer/v2022dev0/app-dev.html",]
-outputs = [ "html", "pdf-in",]
-date = "2016-04-22"
-+++
-
-Apertis is a next generation in-vehicle infotainment platform and SDK. It is an innovative operating system created for in-vehicle infotainment products. It is based on Linux Ubuntu.
-
-## Required Knowledge
-
-You should familiarise yourself with the [development environment in the SDK]( {{< ref "sdk-usage.md" >}} ) before continuing.
-
-To understand and develop Apertis applications, you need to be comfortable with the following topics, libraries and tools:
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-* C Programming
-
-* GLib
-
-* GIO
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-* GObject (Glib Object System)
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-* Clutter
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-* GStreamer
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-* Automake
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-The resources listed below are good references to get started on these topics:
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-* [GObject Wikipedia Page](http://en.wikipedia.org/wiki/GObject)
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-* [GObject tutorial](https://developer.gnome.org/gobject/stable/howto-gobject.html)
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-* [GObject Reference Manual](http://library.gnome.org/devel/gobject/stable)
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-* [GLib Reference Manual](https://developer.gnome.org/glib/stable/)
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-* [GIO Reference Manual](https://developer.gnome.org/gio/stable/)
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-* [Clutter Tutorial](https://wiki.gnome.org/Projects/Clutter/Tutorial)
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-* [Clutter Project Wiki](https://wiki.gnome.org/Projects/Clutter)
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-* [GNU Automake](http://www.gnu.org/software/automake/)
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-* [GObject generator](https://github.com/GNOME/turbine/blob/master)
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-When creating a new project with the Apertis Eclipse plugin, sample application projects are available in "/home/user/sample-applications" path which can be imported for further reference.
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-Having said that, it is essential to have a basic understanding of the GObject and Apertis framework to be able to develop applications. Please use the links to gain a basic understanding of the GObject framework and read the subsequent section for an understanding of the code flow in the HelloWorld example code.
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-# Next
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-- **Ready to build your first app?** Continue on to building a [Hello World app]( {{< ref "appdev-hello-world.md" >}} ).