Fixes for YOLO indices, file formats and paths with special characters

[dpservis]

• Fixrs float indices in YOLO export
• Fixes opening webp
• Fixes opening image file paths with special characters

[dpservis]

A UT seems to fail but my simple test and working code succeed

[alexheat]

Thank you for your contribution @dpservis. I finally had time to look into this.
I figured out why the change was failing the validation tests. Using your method, grayscale images returned an array with only 2 values from the .shape property. (No value for the number of channels.)

I use this code to workaround the issue:

            # If the image is grayscale then there is no img_depth
            if len(im.shape) == 2:
                img_depth = 1
            else:
                img_depth = im.shape[2]  # 3 for color images