[fix] include all outsidescv things only when not on a boundary

See merge request !785

[feature/binarycoefficients-h2o-ch4] Moved binary coefficents for H2O-CH4 from devel to stable

See merge request !784

[fix] path to vtkoutputfields after renaming of folder

See merge request !783

[2p2c] fix construction of interaction volume

See merge request !782

Cleanup/nonequilibrium constraintsolver

See merge request !780

Feature/mpnc 2p2c comparison

See merge request !781

fix/adaptivity

See merge request !776

[test] use CMake guard for test requiring dune-foamgrid

See merge request !778

[linearSolver] Add version check to avoid deprecation warning

See merge request !777

[staggered] fix StaggeredNewtonController for use with Dune 2.5

See merge request !779

The function `min` of the `CollectiveCommunication` looks like this
in Dune 2.5:

```
    template<typename T>
    T min (T& in) const
    {
      T out;
```

In the `StaggeredNewtonController` this has been called like this:

```
    const bool converged = solveLinearSystem_...
    int convergedRemote = converged;
    if (this->comm().size() > 1)
        convergedRemote = this->comm().min(converged);
```

Thus, `T` is determined to be `const bool` and setting `T out;`
without initializing it doesn't work (fortunately). Fix by using
`bool` instead of `const bool`.

In Dune 2.6, the same function looks like that:

```
    template<typename T>
    T min (const T& in) const
```

Therefore, `T` is deduced to be `bool` and everything works fine.
Still does after the change.

* dune-istl has unified SeqILU0 and SeqILUn to SeqILU

The default also assumes one hanging node per scvf such that the adaptive
test work again.

Feature/primaryvariables numeqvector

See merge request !766

[fluxvars] introduce enabled/disabled specific flux specializations

See merge request !763

[tpfa] remove obsolete includes

See merge request !765

Cleanup/mpfa

See merge request !774