Doc: Rearrange files in the doc folder

Source and configuration files for each manual are now located in a
separate subdirectory, with common configuration files in doc/config.

doc
|_config
|_qtcreator
|_qtcreatordev
|_qtdesignstudio

Edit the config files accordingly.

Change-Id: Idc747a7c16e84f3e06add91234dc5fc908e64cc5
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

doc/qtcreatordev/src/creating-plugins.qdoc

@@ -0,0 +1,76 @@
+/****************************************************************************
+**
+** Copyright (C) 2016 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the Qt Creator documentation.
+**
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Free Documentation License Usage
+** Alternatively, this file may be used under the terms of the GNU Free
+** Documentation License version 1.3 as published by the Free Software
+** Foundation and appearing in the file included in the packaging of
+** this file. Please review the following information to ensure
+** the GNU Free Documentation License version 1.3 requirements
+** will be met: https://www.gnu.org/licenses/fdl-1.3.html.
+**
+****************************************************************************/
+
+/*!
+    \page creating-plugins.html
+    \title Creating Plugins
+
+    At its very core, \QC consists of a plugin loader that loads and runs a set
+    of plugins, which then actually provide the functionality that you know from
+    \QC the IDE. So, even the main application window and menus are all provided
+    by plugins. Plugins can use different means to provide other plugins access
+    to their functionality and to allow them to extend certain aspects of the
+    application.
+
+    For example the \c Core plugin, which is the very basic plugin that must be
+    present for \QC to run at all, provides the main window itself, and API
+    for adding menu items, modes, editor types, navigation panels and many other
+    things.
+
+    The \c TextEditor plugin provides a framework and base implementation for
+    different text editors with highlighting, completion and folding, that is
+    then used by other plugins to add more specialized text editor types to \QC,
+    like for editing C/C++ or \c {.pro} files.
+
+    After reading this guide you will know what a basic plugin consists of,
+    how to write a plugin specification file, what the lifecycle of a plugin is,
+    what the general principles for extending existing plugins' functionality
+    and providing interfaces for other plugins are, and will be able to write
+    your first plugin.
+
+    \section1 Basics
+
+    \list
+        \li \l{Getting and Building Qt Creator}
+        \li \l{Creating Your First Plugin}
+        \li \l{Plugin Meta Data}
+        \li \l{Plugin Life Cycle}
+    \endlist
+
+    \section1 Design Principles
+
+    \list
+        \li \l{The Plugin Manager, the Object Pool, and Registered Objects}
+        \li \l{Aggregations}
+        \li \l{Extending and Providing Interfaces}
+    \endlist
+
+    \section1 Creating 3rd-Party Plugins
+
+    \list
+        \li \l{A Note on Binary Compatibility}
+        \li \l{Creating User-Installable Plugins}
+    \endlist
+*/