Creation of a CoupleSolidModel to handle Poro-Solid-Damage models.

[CusiniM]

This PR is related to #1422

Rebaseline: https://github.com/GEOSX/integratedTests/pull/141

Integrated tests work on Lassen.

In my opinion the design works quite well. I have added the permeability models to this PR although they will only be used in #1311.
In a few words, I have created a base class template called CoupledSolid which owns method to access

• a porosity model
• a solid model
• a permeability model.

template< typename SOLID_TYPE, typename PORO_TYPE, typename PERM_TYPE >
class CoupledSolid : public ConstitutiveBase
{
public:
        ...
protected:
  SOLID_TYPE const & getSolidModel() const
  { return this->getParent().template getGroup< SOLID_TYPE >( m_solidModelName ); }

  PORO_TYPE const & getPorosityModel() const
  { return this->getParent().template getGroup< PORO_TYPE >( m_porosityModelName ); }

  PERM_TYPE const & getPermModel() const
  { return this->getParent().template getGroup< PERM_TYPE >( m_permeabilityModelName ); }

  // the name of the solid model
  string m_solidModelName;

  // the name of the porosity model
  string m_porosityModelName;
  
  // the name of the permeability model
  string m_permeabilityModelName;
 };

Then, I have created 2 specialized classes:

• PorousSolid which always has a BiotPorosity and is used solely for Poromechanics
• CompressibleSolid which can have various porosity models and, for now, assumes a nullModel for the solid Model so that all mechanics data (e.g. stresses) are not allocated. This model is what we would use for simulations without mechanics.

For now, the damage can stay as it is ( I think) and the SOLID_TYPE can simply be a Damage etc...

Thus both the PorousSolid and the CompressibleSolid would be

template< typename SOLID_TYPE >
class PorousSolid : public CoupledSolid< SOLID_TYPE, BiotPorosity, StrainDependentPermeability >

template< typename PORO_TYPE,  typename PERM_TYPE >
class CompressibleSolid : public CoupledSolid< NullModel, PORO_TYPE, PERM_TYPE >

I am registering a PorousSolid for each type of SolidModel so that the proper solid model gets instantiated based on the input, i.e.

</PoroElasticIsotropic
   name="porousSolidName"
   solidName="solidModelName"
   porosityName="poroName"
   permeabilityName="permName"
   />
   
</ElasticIsotropic
  name="solidName"
  ...
   />
   
 </BiotPorosity
  name="poroName"
  ...
   />
  </StrainDependentPermeability
  name="permName"
  ...
   />

will automatically instantiate a PorousSolid< ElasticIsotropic > which will be a CoupledSolid<ElasticIsotropic, BiotPorosity, StrainDependentPermeability>.

The same thing could be done for the CompressibleSolid with various porosity and permeability models (I think special model could be used for very specific physics, e.g., chemical reactions that change the porosity).

[TotoGaz]

Nothing really smart, just small C++ comments, nothing about architecture.