Various Audition Improvements

[shaycrk]

This PR includes a few overdue improvements to audition:

• Remove the redundant "tutorial" and "example" notebooks
• Support for baseline models that will be included on graphs regardless of filtering but excluded from model selection
• Remove alpha for selection rule plots (which was making different rules hard to distinguish)
• Ensure stable colors for model types when plotting even after some are filtered out

[nanounanue]

Excellent!