Make FEAssembler store a const reference of the basis
... rather than a copy. This allows to assemble with bases that are not copyable, as for example the RaviartThomasBasis
See https://gitlab.dune-project.org/staging/dune-functions/-/issues/58
... rather than a copy. This allows to assemble with bases that are not copyable, as for example the RaviartThomasBasis
See https://gitlab.dune-project.org/staging/dune-functions/-/issues/58