Renamed phiAlpha -P alphaPhi for consistency with Euler-Euler solvers

...ions/solvers/multiphase/compressibleInterFoam/alphaEqns.H

...terFoam/multiphaseMixtureThermo/multiphaseMixtureThermo.C

applications/solvers/multiphase/driftFluxFoam/alphaEqn.H

...tions/solvers/multiphase/driftFluxFoam/alphaEqnSubCycle.H

applications/solvers/multiphase/driftFluxFoam/createFields.H

applications/solvers/multiphase/interFoam/alphaEqn.H

applications/solvers/multiphase/interFoam/createFields.H

.../solvers/multiphase/interFoam/interMixingFoam/alphaEqns.H

...ations/solvers/multiphase/interPhaseChangeFoam/alphaEqn.H

...multiphaseInterFoam/multiphaseMixture/multiphaseMixture.C

...cations/solvers/multiphase/twoLiquidMixingFoam/alphaEqn.H