Shaders examples do not run at all

The shaders examples have been refactored and now don't work. There were four of them, all slight variations on a theme, with "teapot" and "shader" in the name.

These have been combined into a tabbed QML UI that is meant to display all four, and allow tabbing between.

However the app does not seem to display anything on the screen, and displays a "bad app" icon under Mac.