fvOptions: Corrected docs: 'fieldName' -> 'fields'

Resolves bug-report http://bugs.openfoam.org/view.php?id=2273

src/fvOptions/sources/derived/actuationDiskSource/actuationDiskSource.H

@@ -49,7 +49,7 @@ Usage
     \verbatim
     actuationDiskSourceCoeffs
     {
-        fieldNames      (U);        // names of fields to apply source
+        fields          (U);        // names of fields to apply source
         diskDir         (-1 0 0);   // disk direction
         Cp              0.1;        // power coefficient
         Ct              0.5;        // thrust coefficient

src/fvOptions/sources/derived/buoyancyEnergy/buoyancyEnergy.H

@@ -33,7 +33,7 @@ Usage
     \verbatim
     buoyancyEnergyCoeffs
     {
-        fieldNames      (h);                    // Name of energy field
+        fields          (h);                    // Name of energy field
     }
     \endverbatim
 

src/fvOptions/sources/derived/buoyancyForce/buoyancyForce.H

@@ -33,7 +33,7 @@ Usage
     \verbatim
     buoyancyForceCoeffs
     {
-        fieldNames      (U);                    // Name of velocity field
+        fields          (U);                    // Name of velocity field
     }
     \endverbatim
 

src/fvOptions/sources/derived/meanVelocityForce/meanVelocityForce.H

@@ -36,7 +36,7 @@ Usage
     meanVelocityForceCoeffs
     {
         selectionMode   all;                    // Apply force to all cells
-        fieldNames      (U);                    // Name of velocity field
+        fields          (U);                    // Name of velocity field
         Ubar            (10.0 0 0);             // Desired mean velocity
         relaxation      0.2;                    // Optional relaxation factor
     }

src/fvOptions/sources/derived/meanVelocityForce/patchMeanVelocityForce/patchMeanVelocityForce.H

@@ -36,7 +36,7 @@ Usage
     patchMeanVelocityForceCoeffs
     {
         selectionMode   all;                    // Apply force to all cells
-        fieldNames      (U);                    // Name of velocity field
+        fields          (U);                    // Name of velocity field
         patch           inlet;                  // Name of the patch
         Ubar            (10.0 0 0);             // Desired mean velocity
         relaxation      0.2;                    // Optional relaxation factor

src/fvOptions/sources/derived/rotorDiskSource/rotorDiskSource.H

@@ -35,7 +35,7 @@ Usage
     \verbatim
     rotorDiskSourceCoeffs
     {
-        fieldNames      (U);    // names of fields on which to apply source
+        fields          (U);    // names of fields on which to apply source
         nBlades         3;      // number of blades
         tipEffect       0.96;   // normalised radius above which lift = 0