Add 'ConstrainedMatrix' and 'ConstrainedBitVector' to linearizations
requested to merge patrick.jaap_at_tu-dresden.de/dune-tnnmg:add-constrained-types into feature/new_tnnmg
The extended TNNMG step requires these typenames for the LinearSolver constructor. For the build-in linearizations the contrained types are the same as the unconstrained ones. Plus small notation change in tnnmgstep.hh