Use Qt's resource system to store the shader source

The shader source is included inside each comipled binary file. The
OpenGL example also provides its own shader files which overrides
the default. Common shader code is in the 'common' directory and
each example's custom shader is alongside the example's C++ code.

examples/common/example.qrc

@@ -0,0 +1,6 @@
+<!DOCTYPE RCC><RCC version="1.0">
+<qresource>
+	<file>example.vert</file>
+	<file>example.frag</file>
+</qresource>
+</RCC>