Add arbitrary style transfer and yolo examples

[danomatika]

This PR adds the following (cleaned up) examples:

• arbitrary style transfer
• Yolo v4

It has removed the image colorization example which is now in the feature/exmaple_image_colorization branch as the mode output it relatively uninspiring. We can look into this updating later.

I propose squashing this merge as there are tons of tiny commits.

[danomatika]

Also, there are some formatting fixes to other examples etc which I probably should have made to develop directly.

[Jonathhhan]

@danomatika squashing sounds good :)

[danomatika]

@bytosaur Too bad you didn't squash...