Add a conformance test that uses a vertex shader with no frag shader

Add a conformance test that uses a vertex shader with no frag shader

This creates a material which users a layer to override the color of
the rectangle. A simple vertex shader is then created which just
emulates the fixed function pipeline. No fragment shader is
added. This demonstrates a bug where the layer state is getting
ignored when a vertex shader is in use.

http://bugzilla.clutter-project.org/show_bug.cgi?id=2221