This fixes some fallout of the removal of `MultiTypeBlockMatrix::size()`:
By not providing a generic container interface you can no longer use generic
algorithms like indexed for-loops for matrices. One way to work around
this is to implement the `tuple` protocol to make `Hybrid::size()` work again.

For an alternative solution cf. core/dune-common!1209

GCC reported a compiler error. transformMatrix depends on transformMatrixPattern: therefore the latter should be implemented first.

Implement addToDiagonal for scalars (interpreted as 1x1 matrices)

See merge request agnumpde/dune-matrix-vector!12

The gcc-6 Docker image does not exist anymore.

This makes triangularsolvetest.cc pass.

This is required for dune-istl matrices than use scalars to end
the nesting recursion (and not FieldMatrix), like BCRSMatrix<double>.

 "Catching polymorphic type ‘class Dune::Exception’ by value"

Add missing header resize.hh to CMakeLists.txt

See merge request agnumpde/dune-matrix-vector!10

transpose.hh Fixed

See merge request agnumpde/dune-matrix-vector!8

Use modern CI script

See merge request agnumpde/dune-matrix-vector!6

This introduces the same CI script also used in the other agnumpde repositories.

See core/dune-common#77

Feature/organize traits

See merge request !5