* [macOS] configure examples for use with ogre2

- Use ogre2 instead of ogre in examples that do not accept a command line argument
- Enable logger to display additional Ogre information for debugging

Signed-off-by: Rhys Mainwaring <[email protected]>

* [macOS] configure examples for use with ogre2 and update plugin path

- Prevent the Ogre2RenderEngine searching in /usr/local/opt/ogre2.1/lib/OGRE-2.1 for render system plugins

Signed-off-by: Rhys Mainwaring <[email protected]>

* [macOS] add a QML version of the simple_demo

- This is a QML version of the simple_demo. It uses the same approach to rendering to QML as used in ignition-gui Scene3D.
- For macOS there is an upstream dependency on a pending PR in Ogre2-1 for support of the `currentGLContext` flag.
- The core application render thread is based on the Qt Toolkit example:
	- https://code.qt.io/cgit/qt/qtdeclarative.git/tree/examples/quick/scenegraph/textureinthread?h=5.15

Signed-off-by: Rhys Mainwaring <[email protected]>

* [macOS] apply style guide to function and member variable names

Signed-off-by: Rhys Mainwaring <[email protected]>

* [macOS] apply style guide to function parameters

Signed-off-by: Rhys Mainwaring <[email protected]>

* [macOS] cleanup comments and remove dead code

Signed-off-by: Rhys Mainwaring <[email protected]>

* [macOS] incorporate review feedback in simple_demo_qml

- Remove unused section from CMakeLists.txt
- Move using namespace declarations to translation unit scope
- Remove addition separator line
- Use ignmsg instead of std::cout in ThreadRenderer
- Roll back changes to example text_geom

Signed-off-by: Rhys Mainwaring <[email protected]>

* Apply suggestions from code review

Co-authored-by: Alejandro Hernández Cordero <[email protected]>

Signed-off-by: Rhys Mainwaring <[email protected]>

* [macOS] apply code style guide formatting

Signed-off-by: Rhys Mainwaring <[email protected]>

* [macOS] document the IgnitionRenderer class.

Signed-off-by: Rhys Mainwaring <[email protected]>

* [macOS] update the message on the QML overlay

Signed-off-by: Rhys Mainwaring <[email protected]>

* [macOS] modify simple_demo_qml for qt5.12

- Remove QML_NAMED_ELEMENT from ThreadRenderer
- Rename Renderer in QML to ThreadRenderer

Signed-off-by: Rhys Mainwaring <[email protected]>

* [macOS] rollback changes to examples

- Roll back changes to other examples, keeping only simple_demo_qml.

Signed-off-by: Rhys Mainwaring <[email protected]>

* [macOS] remove additional plugin path for macOS

- Remove additional plugin path for macOS.

Signed-off-by: Rhys Mainwaring <[email protected]>

Co-authored-by: Ian Chen <[email protected]>

Signed-off-by: Ian Chen <[email protected]>

* style changes

Signed-off-by: Ian Chen <[email protected]>

* rename files

Signed-off-by: Ian Chen <[email protected]>

* indentation

Signed-off-by: Ian Chen <[email protected]>

Signed-off-by: Ian Chen <[email protected]>