Provide visualization method for GeoTiff

[HowcanoeWang]

trafficstars

>>> dom = idp.GeoTiff("xxxx.tiff")
>>> dom
<matplotlib.pyplot.axes>

For large dom (> 2000x2000), use the subpixels, and only create a 200x200 preview (make grid point lists and point_query for pixel values of these points).

[HowcanoeWang]

May also work if reading the last page of pyramid geotiff.