Move shader code to external files rather than embedded

A bit of CMake code in each example copies the files to the
correct location and Qt loads them from the application's binary
directory.

examples/common/example.vert

@@ -0,0 +1,20 @@
+#version 140
+
+in vec4 position; // This will be the position of the vertex in model-space
+
+// The usual matrices are provided
+uniform mat4 cameraToClipMatrix;
+uniform mat4 worldToCameraMatrix;
+uniform mat4 modelToWorldMatrix;
+
+// This will be used by the fragment shader to calculate flat-shaded normals. This is an unconventional approach
+// but we use it in this example framework because not all surface extractor generate surface normals.
+out vec4 worldPosition;
+
+void main()
+{
+	// Standard sequence of OpenGL transformations.
+	worldPosition = modelToWorldMatrix * position;
+	vec4 cameraPosition = worldToCameraMatrix * worldPosition;
+	gl_Position = cameraToClipMatrix * cameraPosition;
+}