gray matrix issue resolved

Addresses Issue #435 
and also added test for virtualCamera referencing issue.

    img = Image('lenna')
    b = img.getGrayscalMatrix()
    newimg = Image(b, colorSpace=ColorSpace.GRAY)
    newimg.show()
    newimg.toRGB() # warning because it is grayscale

Signed-off-by: jayrambhia <jayrambhia777@gmail.com>