ShaderEffect should support uniform value arrays

QML ShaderEffect does not support passing array types to shaders as uniform arrays. For example, this would be useful when writing a shader to display precomputed histogram data.

The only available workaround is to put data into a QImage, and pass this to the shader as sampler2D.

QQuickCustomMaterialShader::updateState should be extended to handle array-like types and pass these to the program with QGLShaderProgram::setUniformValueArray.