Fix for skimage and new script to process a batch of inputs

[timhf]

Hey, I used your tool to do some robustness evaluation of BDD100k. Thereby, I came across an error that I fixed: It looks like newer versions of skimage deprecated the multichannel parameter for gaussian. I updated it to channel_axis=-1 according to the docu. I also added a script that is able to apply corruptions to a batch of images, e.g., an entire dataset. If you find this useful feel free to add it to the upstream.

Thanks Tim