Arrange variables according to a defined order. This makes
sure that a c14_date_list always appears with the same
outline.
A c14_date_list has at least the columns c14age
and c14std. Beyond that there's a selection of additional
variables depending on the input from the source databases, as a
result of the c14bazAAR functions or added by other data
analysis steps. This function arranges the expected variables in
a distinct, predefined order. Undefined variables are added at the
end.