V prediction ddim (#1313)
* v diffusion support for ddpm
* quality and style
* variable name consistency
* missing base case
* pass prediction type along in the pipeline
* put prediction type in scheduler config
* style
* try to train on ddim
* changes to ddim
* ddim v prediction works to train butterflies example
* fix bad merge, style and quality
* try to fix broken doc strings
* second pass
* one more
* white space
* Update src/diffusers/schedulers/scheduling_ddim.py
* remove extra lines
* Update src/diffusers/schedulers/scheduling_ddim.py
Co-authored-by: Ben Glickenhaus <ben@mail.cs.umass.edu>
Co-authored-by: Nathan Lambert <nathan@huggingface.co>
