#260 & #49: switch to TypeScript

[ntseng]

Summary

Very unfinished, but leaving the draft here for early feedback and viewing progress over time.

• change package type from commonjs to module
• rewrite most files to use TypeScript
• rework runMode logic
  • add run mode to all logging timestamps
  • check for dev mode instead of prod mode (test mode is "pretending to be" prod mode)
  • make enum for run modes
  • pass isDevMode boolean instead of entire mode enum
• Fix model configuration so that types populate to instances #49: add property type declarations to models

Local Tests Performed

• bot still turns on (no build errors, circular dependencies, or start-up errors)
• Require full regression test for released version

Issue

Closes #260
Closes #49