ENH: added surfaceFieldValue uniformity operation

...s/field/fieldValues/surfaceFieldValue/surfaceFieldValue.C

...s/field/fieldValues/surfaceFieldValue/surfaceFieldValue.H

...ieldValues/surfaceFieldValue/surfaceFieldValueTemplates.C

tutorials/compressible/rhoSimpleFoam/squareBend/0/T

tutorials/compressible/rhoSimpleFoam/squareBend/0/U

tutorials/compressible/rhoSimpleFoam/squareBend/0/alphat

tutorials/compressible/rhoSimpleFoam/squareBend/0/epsilon

tutorials/compressible/rhoSimpleFoam/squareBend/0/k

tutorials/compressible/rhoSimpleFoam/squareBend/0/nut

tutorials/compressible/rhoSimpleFoam/squareBend/0/p

.../compressible/rhoSimpleFoam/squareBend/system/controlDict

...ompressible/rhoSimpleFoam/squareBend/system/fieldTransfer

...mpressible/rhoSimpleFoam/squareBend/system/sampleControls

...als/compressible/rhoSimpleFoam/squareBend/system/sampling