Fixes for the dune-fem linear solver backend#1

Merged

dr-robertk merged 3 commits intodr-robertk:PR/fem-solver-backendfrom andlaus:fix_fem_solver_backend

Jun 14, 2019

Commits on May 28, 2019

[feature][solver] This adds a FemSolverBackend and the

Robert Kloefkorn
authored and
andlaus
committed
WIP: cleanup the backend for the dune-FEM linear solvers
andlaus
committed
let the linear solver backend determine the type of the sparse matrix adapter
andlaus
committed