Fix comment error that makes understanding scheduling more confusing.

allow first pass and hires pass to use a single prompt to do different prompt editing, hires is 1.0..2.0:
  relative time range is [1..2]
  absolute time range is [steps+1..steps+hire_steps], e.g. with 30 steps and 20 hires steps, '20' is 2/3rds through first pass, and 40 is halfway through hires pass

Fix composable diffusion weight parsing

revert SD2.1 back to use the original repo
add SDXL's force_zero_embeddings to negative prompt

assoicated -> associated

added support for AND from https://energy-based-model.github.io/Compositional-Visual-Generation-with-Composable-Diffusion-Models/

Only build the parser once (at import time) instead of for each step.

doctest is run by simply executing modules/prompt_parser.py