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/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())