OSspecific: altered file tests

- removed the previously added fileName type(), isDir(), isFile() methods.

- added optional bool parameter to isFile() function to explicitly
  enable/disable the check for gzip files.

- fixed minor bugginess where the default usage of isFile() would result in
  false positive matches.

- be slightly more stringent and use isDir() and isFile() instead of
  exists() function when we actually know the expected type.

applications/utilities/parallelProcessing/reconstructParMesh/reconstructParMesh.C

@@ -355,7 +355,7 @@ int main(int argc, char *argv[])
 
     while
     (
-        exists
+        isDir
         (
             args.rootPath()
           / args.caseName()