ENH: Adding evaporation-condensation lagragian model for solution

1) Adding LiquidEvapFuchsKnudsen model for lagrangian evaporation.
   This models is based on a diffusion type of evaporation/
   condensation on particles composed of solution (liquid + solid).

2) Adding modes of calculating the particle rho and volume change.
   The new keyword in constantProperties is 'volumeUpdateMethod'
   which three options:
        a) constantRho
        b) constantVolume
        c) updateRhoAndVol

   The old keyword 'constantVolume' true/face is still valid

3) The entry rho0 is now optional for multicomponent parcels.
   If defined , it is used, but if it is not the actual mixture
   provided is used to calculate rho0 of the particle.
   T0 is still used as initial T and Cp0 is over-written in the
   multicomponent cloud but still required.

4) Adding tutorial for evaporation/condensation model

tutorials/lagrangian/reactingParcelFoam/rectangularChannel/system/fvSolution

@@ -0,0 +1,112 @@
+/*--------------------------------*- C++ -*----------------------------------*\
+| =========                 |                                                 |
+| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
+|  \\    /   O peration     | Version:  v1806                                 |
+|   \\  /    A nd           | Web:      www.OpenFOAM.com                      |
+|    \\/     M anipulation  |                                                 |
+\*---------------------------------------------------------------------------*/
+FoamFile
+{
+    version     2.0;
+    format      ascii;
+    class       dictionary;
+    location    "system";
+    object      fvSolution;
+}
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+solvers
+{
+    rho
+    {
+        solver          PCG;
+        preconditioner  DIC;
+        tolerance       1e-05;
+        relTol          0.1;
+    }
+
+    rhoFinal
+    {
+        $rho;
+        tolerance       1e-05;
+        relTol          0;
+    }
+
+    "(U|k|epsilon)"
+    {
+        solver          smoothSolver;
+        smoother        symGaussSeidel;
+        tolerance       1e-06;
+        relTol          0.1;
+    }
+
+    "(U|k|epsilon|omega)Final"
+    {
+        $U;
+        tolerance       1e-06;
+        relTol          0;
+    }
+
+    p_rgh
+    {
+        solver          GAMG;
+        tolerance       0;
+        relTol          0.1;
+        smoother        GaussSeidel;
+    }
+
+    p_rghFinal
+    {
+        $p_rgh;
+        tolerance       1e-06;
+        relTol          0;
+    }
+
+    "(Yi|O2|N2|H2O)"
+    {
+        solver          PBiCGStab;
+        preconditioner  DILU;
+        tolerance       1e-6;
+        relTol          0;
+    }
+
+    h
+    {
+        $Yi;
+        relTol          0.1;
+    }
+
+    hFinal
+    {
+        $Yi;
+    }
+}
+
+potentialFlow
+{
+    nNonOrthogonalCorrectors 5;
+}
+
+
+PIMPLE
+{
+    transonic       no;
+    nOuterCorrectors 1;
+    nCorrectors     2;
+    nNonOrthogonalCorrectors 0;
+    momentumPredictor yes;
+}
+
+relaxationFactors
+{
+    fields
+    {
+    }
+    equations
+    {
+        ".*"            1;
+    }
+}
+
+
+// ************************************************************************* //