MyPy Migration

[AdamGagorik]

Rewrite the codebase to use type annotations.

• MyPy migration
• Change workers into dataclass
• Add unit tests for manager
• Add unit test for refill app
• Add unit test for cleaner
• Fix error in items.csv
• Add test to load default items.csv
• Add constants for PATHs
• Add function to test if database connection can be made
• Add advanced python scheduler
• Run broker using APS
• Add ability to use sqlite to existing apps
• Ignore .db files
• Fix mypy warnings
• Try to fix kwargs for broker