ENH: use static to define default blockMesh verbosity

- make handling of verbosity more consistent.

  Make all setter return the old value, remove (unused) default
  parameter as being counter-intuitive.  This makes it easier to
  restore the original values.

  For example,

     const bool oldVerbose = sampler.verbose(false);
     ...
     sampler.verbose(oldVerbose);

src/functionObjects/field/Curle/Curle.C

@@ -169,7 +169,7 @@ bool Foam::functionObjects::Curle::read(const dictionary& dict)
             );
 
             // Use outputDir/TIME/surface-name
-            surfaceWriterPtr_->useTimeDir() = true;
+            surfaceWriterPtr_->useTimeDir(true);
         }
     }
 

src/functionObjects/field/fieldValues/surfaceFieldValue/surfaceFieldValue.C

@@ -969,7 +969,7 @@ bool Foam::functionObjects::fieldValues::surfaceFieldValue::read
 
         if (debug)
         {
-            surfaceWriterPtr_->verbose() = true;
+            surfaceWriterPtr_->verbose(true);
         }
 
         if (surfaceWriterPtr_->enabled())

src/functionObjects/utilities/areaWrite/areaWrite.C

@@ -109,9 +109,11 @@ Foam::areaWrite::areaWrite
 
 // * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
 
-void Foam::areaWrite::verbose(const bool verbosity)
+bool Foam::areaWrite::verbose(const bool on)
 {
-    verbose_ = verbosity;
+    bool old(verbose_);
+    verbose_ = on;
+    return old;
 }
 
 
@@ -188,8 +190,8 @@ bool Foam::areaWrite::read(const dictionary& dict)
         auto surfWriter = surfaceWriter::New(writerType, writerOptions);
 
         // Use outputDir/TIME/surface-name
-        surfWriter->useTimeDir() = true;
-        surfWriter->verbose() = verbose_;
+        surfWriter->useTimeDir(true);
+        surfWriter->verbose(verbose_);
 
         writers_.set(areaName, surfWriter);
     }

src/functionObjects/utilities/areaWrite/areaWrite.H

@@ -205,8 +205,9 @@ public:
 
     // Member Functions
 
-        //- Set verbosity level
-        void verbose(const bool verbosity = true);
+        //- Enable/disable verbose output
+        //  \return old value
+        bool verbose(const bool on);
 
         //- Read the areaWrite dictionary
         virtual bool read(const dictionary& dict);