Third phase of Parameters API redesign: drop Calculator.from_file.
Third phase of Parameters API redesign: drop Calculator.from_file.

This classmethod appears to not be used in the webapp repo; dropping
it does not change the four (out of 78) taxcalc test failures.
Dropping Calculator.from_file requires minor changes to the
Calculator.__init__ method, which now treats the params argument in
the same way as the records argument is treated.

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