Feature/functions interface 2.5-compatible

Christian Engwerrequested to merge
feature/functions-2.5 into master

This is a cleanup of !114 (closed).

Feature:

  • a wrapper class to implement a dune-functions compatible functions interface using old-style pdelab functions
  • interpolate from old-style functions and callables
  • add a dune-functions compatible Dune::PDELab::DiscreteGridViewFunction
  • a free function makeLocalFunctionTree to transform trees if old-style functions, trees of callables or trees of dune-functions functions int local functions

Furthermore I suggest do deprecate the old-style functions

Merge request reports