add a isPopulated variable in datatable and dtype  on get_value of a Column
add a isPopulated variable in datatable and dtype  on get_value of a Column

sgmap/openfisca-core,benjello/openfisca-core,openfisca/openfisca-core,benjello/openfisca-core,adrienpacifico/openfisca-core,openfisca/openfisca-core