[feature/el2pdecoupled] Current version, including simple problem for measuring the computational effort

Time-step increases on suggestion by NewtonController

Simplified required input: Same DtInitial for all subproblems

MAJOR
Flow
2pccelementvolumevariables:
Got rid of unnecessary scvIdx Loop
Calculate bulk modulus from lamda and mu

Mechanics:
Mechanics part works for both CC and Box in the transport problem
Distinction in the model and the localoperator made using
PROBLEM_IS_CC in the cc-file

spatialparams adapted so different properties can be set for
caprock and fault

MINOR
MaterialLaw can be plotted

Changes to make results match with Antonio/TOUGH2

Option to change wetting/nonwetting in the input file
Option to use of pore compr./fixed stress in the input file
Option to change CC/Box in cc file

First adaptions for a matching CO2 test case (tables containing Ant)

Whether the pore compressibility is used or not can be specified in the input file

One spatialparams file for el and 2p
Replaced repeated if statement to distinguish between fault and matrix by
function isInFault

on communication with Jonny

MODEL
2p
2pelementvolumevariables.hh: Contains fixed stress approach calculating an
effective porosity difference
In addition, there are two version for box and cc
2pvolumevariables: No need to define effPorosity_, as this is done in the
elementvolumevariables
2pfluxvariables.hh: Changed porosity law (after talking to Jonny)
nonlinear/newtoncontroller.hh: Finer line search for 2p-fixed stress
nonlinear/newtonmethod.hh: Store last Solution uLastIter

el
model.hh: Changed porosity law (after talking to Jonny)
elementvolumevariables.hh: Changed porosity law, renamed scvCenter to scvCenterGlobal
localoperator:hh numScv from fvGeometry.numScv; and not from eg.entity().subEntities(dim),
made further adaption necessary
el2p/newtoncontroller.hh: Possibility to use a damped update
el2p/basemodel.hh: Include storing the last iteration to be able to compare the
change between iterations

Other
implicit/model.hh: Function to return uLastIter

Minor:
2pmodel.hh: vtu files contain porosity now
2plocalresidual.hh: No changes, just different output to the screen
fluxvariables.hh: Renamed from ElTwoPFluxVariables to DecoupledElasticFluxVariables
propertydefaults.hh: Renamed too

TEST
decoupled2pproblem.hh: Minor changes, use same time descritisation as Jonny
decoupledelasticproblem.hh: Minor changes, use same time descritisation as Jonny
decoupled2pspatialparams.hh: Defined different spatialparams for fault and
matrix (as in the elastic part), introduced pore compressibility
decoupledelastic2pproblem.hh: Fixed stress architecture instead of damping

First version of a decoupled flow and geomechanics model including a
respective test. Derived from the fully coupled el2p model.

[doc] Fix "coefficent" typo

See merge request !468

[Readme] Reference dumux logo

See merge request !474

[freeflow] Add files for estimating the properties of a turbulence flow

See merge request !463

[gnuplotinterface] Various improvements

See merge request !471

* enable dashed lines via useDashedLines
* .gp only if specified
* use C++ function for converting to string
* cleanup

[dumux][cleanup] Remove deprecation warnings

See merge request !460

[fluidsystems][h2oair] Implement relative humidity

See merge request !464

Bump version 2.12-git

See merge request !465

[2cstokes2p2c] Provide possibility to use molar based formulation for coupled problems

See merge request !462

[dumuxmessage] Cleanup start message the current master isn't the birthday edition anymore

See merge request !461

fix CHANGELOG.md

See merge request !459

[fix] Remove superfluous semicolons

See merge request !457

Update CHANGELOG.md

See merge request !441