Refactoring

[p3zo]

Mostly general refactoring for usability & maintainability, notably:

• Usage instructions
• Documentation for all descriptors
• Add a setup file so the library can be easily installed with pip
• Simplify the entry-point while maintaining backwards-compatibility
• Returned descriptors in a dict of {descriptor_name: descriptor_value}
• Standardize formatting, code style, and function signatures
• Merge low/mid/hi functions to reduce redundant code
• Delete txt and style files used specifically for Daniel's PhD
• Separate descriptors that should only be calculated for 16-step patterns
• Resample all inputs to a 16th note resolution, or 4 ticks per beat in MIDI terms

Also some functional & performance changes, notably:

• Replace pattlists with piano roll np.arrays as the internal representation of patterns
• Use vector operations in place of nested for-loops
• Avoid zero division when pattern has no onsets
• Reduce redundant function calls

The resulting performance speed-up of all changes combined is ~8700x.