STYLE: minor adjustments for code formatting and comments

src/functionObjects/field/fieldAverage/fieldAverage.C

src/functionObjects/field/fieldAverage/fieldAverage.H

...unctionObjects/field/fieldAverage/fieldAverageTemplates.C

src/functionObjects/field/fieldExpression/fieldExpression.C

src/functionObjects/field/fieldExpression/fieldExpression.H

...nObjects/field/fieldExpression/fieldExpressionTemplates.C

...functionObjects/field/fieldsExpression/fieldsExpression.C

...functionObjects/field/fieldsExpression/fieldsExpression.H

...bjects/field/fieldsExpression/fieldsExpressionTemplates.C

src/functionObjects/field/fluxSummary/fluxSummary.C

src/functionObjects/field/fluxSummary/fluxSummary.H

src/functionObjects/field/grad/grad.C

src/functionObjects/field/grad/grad.H

src/functionObjects/field/grad/gradTemplates.C

src/functionObjects/field/mag/mag.C

src/functionObjects/field/mag/mag.H

src/functionObjects/field/mag/magTemplates.C

src/functionObjects/field/magSqr/magSqr.C

src/functionObjects/field/magSqr/magSqr.H

src/functionObjects/field/magSqr/magSqrTemplates.C