dataset.py and polygonize.py: enable for proper TIFF image processing

[MarkusKoenig73]

if images have been processed as TIFF images instead of JPEG (createDataSpaceNet.py) :

---

dataset.py:
replace('.tif', 'segcls.png')

polygonize.py:

when iterating through files:
#image_files = [image_file for image_file in image_files if image_file.endswith('.jpg')] #.tif since i produced files in tif format using script createDataSpaceNet.py
image_files = [image_file for image_file in image_files if ( image_file.endswith('.tif') and (not (image_file.endswith('segcls.tif')) and (not (image_file.endswith('segobj.tif'))) ) )]

and

#image_name_no_file_type = image_name.split('.jpg')[0]
image_name_no_file_type = image_name.split('.tif')[0]