InvokeAI: Tracker for breaking bugs in new webUI

@lstein, @psychedelicious, @Kyle0654, @netsvetaev (apologies if I missed anyone)

Describe your environment These bugs should occur on any platform

Describe the bug

1. Reproducer: python backend/server.py

Traceback (most recent call last):
  File "C:\Users\quaestor\Source\stable-diffusion-stable\backend\server.py", line 22, in <module>
    from ldm.dream.pngwriter import PngWriter, PromptFormatter
ImportError: cannot import name 'PromptFormatter' from 'ldm.dream.pngwriter' (c:\users\quaestor\source\stable-diffusion-stable\ldm\dream\pngwriter.py)

1. Reproducer: attempt to generate an image

Traceback (most recent call last):
  File "C:\Users\quaestor\Source\stable-diffusion-stable\backend\server.py", line 375, in generate_images
    model.prompt2image(
  File "c:\users\quaestor\source\stable-diffusion-stable\ldm\generate.py", line 344, in prompt2image
    results = generator.generate(
  File "c:\users\quaestor\source\stable-diffusion-stable\ldm\dream\generator\base.py", line 73, in generate
    image_callback(image, seed)
  File "C:\Users\quaestor\Source\stable-diffusion-stable\backend\server.py", line 364, in image_done
    path = save_image(image, all_parameters, result_path, postprocessing=postprocessing)
  File "C:\Users\quaestor\Source\stable-diffusion-stable\backend\server.py", line 310, in save_image
    path = pngwriter.save_image_and_prompt_to_png(image, command, filename)
TypeError: PngWriter.save_image_and_prompt_to_png() missing 1 required positional argument: 'name'

Additional context This is a tracker for bugs relating to the recent web UI work. Obviously it is under heavy development, so this is not high-priority work.