Added initial changelog for Qt3D

This is just a output of perl create_changelog.pl ../ v5.6.0...HEAD.
Maintainer, please take this over & do needed modifications. We need
to get this in really soon.

Change-Id: Iaca68d278e3eef098e787fc9cb44df64d55bcbe4
Reviewed-by: Paul Lemire <paul.lemire@kdab.com>
Reviewed-by: Kevin Ottens <kevin.ottens@kdab.com>

dist/changes-5.7.0

@@ -0,0 +1,64 @@
+
+Important Behavior Changes
+--------------------------
+
+ - Cloning subsystem is completely removed, replaced with
+   QNodeCreationChange and QNodeDestroyedChange types.
+ - QSceneChange and subclasses overhauled
+ - QNodeIds are now passed and accepted in QVectors, not QLists.
+ - API cleaned up and made more consistent
+ - Shutdown crashes / races fixed
+ - Qt3DCore, Qt3DRender, Qt3DInput and Qt3DLogic are now stable
+ - New library Qt3DExtras is still unstable (see below)
+
+Render
+------
+
+ - QRenderSettings used to specify frame graph, picking settings
+   and renderer update policy.
+ - Texture loading reimplemented. Supports DDS files containing
+   compressed formats.
+ - Added support for clearing multiple buffers.
+ - Added support for separate blend modes for RGB and Alpha.
+ - Fixed support for base instance argument when using instanced
+   rendering.
+ - Support for compute shaders.
+ - QObjectPicker component high level convenience class for
+   ray-cast based picking.
+
+Input
+-----
+
+ - Added GenericDevice.
+ - Improved API around buttons used as input for axes.
+ - Button controlled axes now support linear ramp up/down
+   curves rather than being binary valued.
+
+Logic
+-----
+
+ - Renamed QLogicComponent to QFrameAction
+
+Scene3D
+-------
+
+ - Provides integration point to embed Qt 3D into a Qt Quick 2
+   scene.
+
+Extras
+------
+
+ - Added unstable Qt3DExtras library to hold higher level sets
+   of elements. This library will change in the future but will
+   offer similar facilities.
+ - To keep Render and Input aspects generic, the Extras lib
+   provides a location to keep experimental higher level utilities
+   such as materials and geometries. It is perfectly possible to
+   use Qt 3D without Qt3DExtras but it can give you a quick start
+   if you do not wish to write your own materials etc.
+ - Provides some default geometries such as QSphereMesh,
+   QCubeMesh, QTorusMesh etc.
+ - Provides some default materials such as QPhongMaterial,
+   QDiffuseMapMaterial etc. along with their associated effects.
+ - Provides some example window integration points.
+ - Provides some example camera controllers.