Fail when column doesn't exist.
Remove useless variable.
Cleanup Bareme __iter__ method.
Copy default legislation to be able to modify actual legislation without changing the default one.
Add tree of columns.
Don't export column freq to JSON when it is 'year'.
Accept enumeration index as string.
Accept string indexs when enumeration column has no enumeration.
Add survey_only attribute to columns.
Improving assert message
Added a survey_onl kwarg for Prestation