Style mixing video and update projection code

[PDillis]

• style_mixing.py: Added the style-mixing video option using lerp; it helps to play with this, as the --col-styles really gives you the power to control what is transferred and what isn't.
• projector.py: Added an option for the projector to set the number of steps as well as to save every step (both the image and dlatent.npy will be saved); I used this for generating a specific latent walk in my models by getting these dlatents and moving through them in a controlled manner, so I hope it's useful for someone else. The next step is to take a dir of images to project, but I'll do that next year.
• generate.py: Minor fixes to code style as well as a bit of optimization; more can be done here, but not a priority.

[dvschultz]

Sorry it looks like I added some content to the generate script which is causing merge conflicts. I’ll try to look at this more this week. appreciate you cleaning up my garbage code :)

[PDillis]

No problem, I was going to fix the merge conflicts myself but then I figured you were toying with other things as well (also my PC died on me). Let me know if you want any help as well, but the code isn't garbage haha, as I said, it's not a priority to 'fix' it.