Seventh phase of Parameters API redesign: alternative default_data().
Seventh phase of Parameters API redesign: alternative default_data().

Add Parameters classmethod default_data(cls, metadata=False,
first_value_year=None) that is intended to replace the legacy
global default_data function in the parameters.py file.

mmessick/Tax-Calculator,mcdeaton13/Tax-Calculator,mmessick/Tax-Calculator,mcdeaton13/Tax-Calculator