Export TypeScript Types, Minor Code Housekeeping

[prescience-data]

Implements:

• Fixes TypeScript exports
• Consolidates dangling types
• Adds typed Exceptions
• Inlines some verbose code
• Adds lint to npm commands

Suggestions:

• Would be good to implement some ESLint rules to avoid contributors IDEs messing with code style (some things that prettier doesn't catch).
• With typed Exceptions added, may be worth adding specific error instanceof checks in certain places.