Add "All Voices" (at Once) Checkbox for Part-Combination Selection

- change "all voice pairs" to "[all pairs]"
- tell Analyzer "[all]" means "all voices at once"
- Also many incidental formatting changes to views/main.py
Optimizations and Fixes in ChordsLists Experiment

- hopefully it's faster...
- now also shows root-and-quality-and-FB when possible
- shows bass-and-FB when there is no "quality" to speak of