Added class for restarting adapted grids

   - reviewed by Bernd

Dumux-Svn-Revison: 10688
Ported-By: Andreas Lauser <andreas.lauser@iws.uni-stuttgart.de>
Decoupled grid adaptive models can now use the restart function

   - writes *.grs files which store the macro grid and the refinement
   - so far, only ALUGrid provides implementations for writing and
     reading grids -> adaptive restart can only be used with ALUGrid
   - reviewed by Bernd

Dumux-Svn-Revison: 10690
Ported-By: Andreas Lauser <andreas.lauser@iws.uni-stuttgart.de>
added the possibility for restricting the size of a new time step in impet models

   - The default value for the Impet.DtVariationRestrictionFactor is
     such that the time-step variation is not restricted. Values between
     zero and one restrict in both directions, values greater than one
     only restrict larger time steps
   - reviewed by Bernd

Dumux-Svn-Revison: 10691
Ported-By: Andreas Lauser <andreas.lauser@iws.uni-stuttgart.de>
More than one pressure value can now be fixed inside the domain if a finite volume pressure model is used.

Additionally, the pressure field is now initialized using the
problem.initial() function. Giving meaningful initializations can
improve the convergence of iterative linear solvers which start the
iterations from the values given in the solution vector

   -reviewed by Bernd

Dumux-Svn-Revison: 10693
Ported-By: Andreas Lauser <andreas.lauser@iws.uni-stuttgart.de>
split of the initializeMatrix() function in the finite volume pressure models of impet schemes

   - This allows the use of the sparse matrix initializations of parent classes and the modification in derived classes
     -> once an end...()-function of the sparse matrix is called it can
     no longer be modified!

     -reviewed by Bernd

Dumux-Svn-Revison: 10695
Ported-By: Andreas Lauser <andreas.lauser@iws.uni-stuttgart.de>
Included a porosity threshold value in the 2p impet model which can be set to avoid porosities which approach zero

   -reviewed by Bernd

Dumux-Svn-Revison: 10697
Ported-By: Andreas Lauser <andreas.lauser@iws.uni-stuttgart.de>
Changed pressEqIdx in the 2pIndices to pressureEqIdx to be consistent with the 2p2c models

Dumux-Svn-Revison: 10698
Ported-By: Andreas Lauser <andreas.lauser@iws.uni-stuttgart.de>
Extended the IMPES scheme to allow for local time-stepping for each flux face of the finite-volume transport model

   - time steps for the pressure model can be choosen larger than for the
     transport model
   - locally small time steps of the std::explicit scheme are less
     restrictive

   - reviewed by Bernd

Dumux-Svn-Revison: 10700
Ported-By: Andreas Lauser <andreas.lauser@iws.uni-stuttgart.de>
Included pressEqIdx again for 2p-IMPES models for backward compatibility. Will be removed after the next release.

Dumux-Svn-Revison: 10702
Ported-By: Andreas Lauser <andreas.lauser@iws.uni-stuttgart.de>
After a grid adaptation the pressure solution vector is now initialized using the old pressure solution -> the solution vector is used as initial guess by iterative linear solvers

Dumux-Svn-Revison: 10705
Ported-By: Andreas Lauser <andreas.lauser@iws.uni-stuttgart.de>
Added additional standard test scenarios for testing the mpfa implementation

Dumux-Svn-Revison: 10706
Ported-By: Andreas Lauser <andreas.lauser@iws.uni-stuttgart.de>
Use correct indices in the problem definition and fixed make headercheck

Dumux-Svn-Revison: 10707
Ported-By: Andreas Lauser <andreas.lauser@iws.uni-stuttgart.de>
fix the decoupled tests