Re-Structure README

[hf-kklein]

The current README is very detailed but also very long.
For new/API users it might be a bit too much/too overwhelming in the way it currently is.
I'd suggest to

• remove the local setup section and only refer to our python_template_repository and the instructions there
• Separate the Terminology into
  1. Terms that are important for devs and for API users (e.g. "ahb expression", "condition expression", parsing vs. evaluation, differnet kinds of compositions)
  2. Terms that are only import for (ahbicht) devs (e.g. "transformer", "grammar", "tree", branches, tokens, UnevalautedFC, EvaluatableFC, etc.)
• also we should make the API calls to our azure function a bit more prominent