added lookupOrAddDefault and readIfPresent functions

...ls/compressible/DeardorffDiffStress/DeardorffDiffStress.C

...ls/compressible/DeardorffDiffStress/DeardorffDiffStress.H

src/LESmodels/compressible/GenEddyVisc/GenEddyVisc.C

src/LESmodels/compressible/GenEddyVisc/GenEddyVisc.H

src/LESmodels/compressible/GenSGSStress/GenSGSStress.C

src/LESmodels/compressible/GenSGSStress/GenSGSStress.H

src/LESmodels/compressible/LESmodel/LESmodel.C

src/LESmodels/compressible/LESmodel/LESmodel.H

src/LESmodels/compressible/Smagorinsky/Smagorinsky.C

src/LESmodels/compressible/Smagorinsky/Smagorinsky.H

src/LESmodels/compressible/SpalartAllmaras/SpalartAllmaras.C

src/LESmodels/compressible/SpalartAllmaras/SpalartAllmaras.H

src/LESmodels/compressible/dynOneEqEddy/dynOneEqEddy.C

src/LESmodels/compressible/lowReOneEqEddy/lowReOneEqEddy.C

src/LESmodels/compressible/lowReOneEqEddy/lowReOneEqEddy.H

src/LESmodels/compressible/oneEqEddy/oneEqEddy.C

src/LESmodels/compressible/oneEqEddy/oneEqEddy.H

.../incompressible/DeardorffDiffStress/DeardorffDiffStress.C

.../incompressible/DeardorffDiffStress/DeardorffDiffStress.H

src/LESmodels/incompressible/GenEddyVisc/GenEddyVisc.C