Add thumbnail images for tutorials.
ADD
tutorials/basic/thumb.jpg
tutorials/basic/thumb.jpg
Binary files /dev/null and b/tutorials/basic/thumb.jpg differ

ADD
tutorials/tile_source/thumb.jpg
tutorials/tile_source/thumb.jpg
Binary files /dev/null and b/tutorials/tile_source/thumb.jpg differ

ADD
tutorials/wms/thumb.jpg
tutorials/wms/thumb.jpg
Binary files /dev/null and b/tutorials/wms/thumb.jpg differ

Add thumbnail images for tutorials.