ShaderEffectItem doesn't expose matrix4x4 properties as valid shader uniforms

ShaderEffectItem makes QTransform properties available in shaders as uniforms, but not QMatrix4x4 properties. In QtQuick2, the "matrix4x4" property type is provided, which is backed by a QMatrix4x4, and these properties should also be accessible in shaders as uniforms, however they are not.

ShaderEffectItem should be fixed.