Correct default for StrCol.
Fix constant_amount taxscale
Fix constant_amount_option
Convert default of enumerations as strings instead of integers.
Fail when an EnumCol has no enum.
Change set_dependencies parameters to not depend of a tax-benefit system anymore.
Accept strings for boolean columns.
Rename from_str (resp. to_str) to legislation_from_str (resp. legislation_to_str).
Remoe trailing space
Add Error when NaNs are created during calculation
Removing unused variable
Remove unwanted variables
Add real_formula attribute to Formula.
Fix parameters to use updated tax_scale methods