Add data validation for rules engine

[jkwan2011]

Input to the rules engine should be validated:

• Move the data models from the test_examples into the rules engine (will require restructuring of test input data)
• Move validation from test_examples into rules engine
• Add new validation as appropriate

[jkwan2011]

• Separate out the data objects into separate classes (e.g., outdoor temperature, billing period usage)
• Evaluate operations performed on data and restructure classes if necessary (for instance, take a look if the functions called in the initialization of BillingPeriod should be moved elsewhere)
• Investigate how fuel data will be input into the rules engine (i.e., will it be parsed by the Javascript or does it need to be validated by the Python)

[jkwan2011]

Data models broken out into #106.

[alanisaac]

Validation is provided by the Pydantic models.