The bases from dune-functions can currently not be used as a drop in
replacement, because the latter do not allow to select the range type
as we did in dune fufem. Before deprecating these, we should either
be sure to a happy with double once and for all, or wait until
dune-functions is fixed and then remove all uses of fufem bases
in fufem itself. Currently the deprecations just clutter the
compiler output and you cannot get rid of this.