[IO-631] Add a CountingFileVisitor (as the basis for a forthcoming

DeletingFileVisitor).

Author: Gary Gregory

src/main/java/org/apache/commons/io/file/CountingFileVisitor.java

@@ -27,6 +27,8 @@
 
 /**
  * Counts files, directories, and sizes, as a visit proceeds.
+ * 
+ * @since 2.7
  */
 public class CountingFileVisitor extends SimpleFileVisitor<Path> {