[headercheck] fix several headers to pass make headercheck

See merge request !800

[typetraits] Implement isValid function to generate class member introspection functors

See merge request !797

* isValid can be used to generate a functor that can check whether an operation done with a type is valid
* this patch also provides examples in form of a test and documentation

Feature/variable eps

See merge request !791

[newton] use new NewtonSolver in incompressible 2p fv test

See merge request !795

[newton] format output consistently

See merge request !793

[newton] fix for use with Dune 2.5

See merge request !792

[nonlinear][NewtonSolver] Fix compilation with g++5

Closes #445

See merge request !794

There seems to be a bug in g++5 which which prevents compilation when
defining the call to the implementation directly to Dune::Hybrid::forEach.

We therefore store this call in a lambda and pass it to the
for loop afterwards.

Use a uniform number of digits for the iteration count as well as
a consistent format for the floating point values.

See !779.

Feature/unify newtoncontrollers

See merge request !762

[test][freeflowMaxwellStephan] Fix test

See merge request !790

* this is the only test that failed after the changes in momentum upwind, thus the use of inertia terms is disabled
* use fixed times to write output
* do some clean-up

[navierstokes] Improve flux variables

See merge request !745

Somehow the upwinding and changes in navierstokes led to an additional Newton step

* rename old test for low Re testing

* introduce upwind weight for momentum flux
* use convenience function to calculate all momentum fluxes
* rename computeNormalMomentumFlux to computeFrontalMomentumFlux
* rename computeTangetialMomentumFlux to computeNormalMomentumFlux
* move pressure term from  local residual to fluxVars
* use separate function to treat outflow boundaries
* improve docu and clean-up

* explicitly check for outflow BC
* small clean-ups
* improve docu

[impes] Remove grid singleton from problem

See merge request !773

* NewtonMethod
* NewtonController

* 1p2c, 2p2c, test_donea (NavierStokes)

* combination of previous NewtonMethod and NewtonController classes
* capable of handling MultiType matrices and vectors
* adapt convergence writer

* updateGridVariables
* resetTimeStep

Fix/mpfa assertions

See merge request !788

unite misciblemultiphaseconstraintsolver and miscible2pncconstraintsolver and…

See merge request !786

[doxygen][fluidsystems] Fix erroneous formula

See merge request !787

unite misciblemultiphaseconstraintsolver and miscible2pncconstraintsolver and deprecate unnecessary constraintsolvers. use misciblemultiphase now in all models