VOL-4836: VOLTHA release prep.

Makefile
--------
  o Update copyright notice.
  o include a few library makefiles for displaying help, etc.
  o Added target sterile to make clean + remove venv.
  o Replace inlined rm -fr, rm -f with make builtin $(RM) && $(RM) -r

tox.ini
-------
  o Add more interpreter versions to envlist so python 3.10.x can be used.

Change-Id: Ideb7e30ff703dff18b707226a4821455f5b1f261
diff --git a/makefiles/lint/license/license-helper.sh b/makefiles/lint/license/license-helper.sh
index 499f854..0f690e4 100755
--- a/makefiles/lint/license/license-helper.sh
+++ b/makefiles/lint/license/license-helper.sh
@@ -1,6 +1,6 @@
 #!/bin/bash
 # -----------------------------------------------------------------------
-# Copyright 2022 Open Networking Foundation
+# Copyright 2022-2023 Open Networking Foundation (ONF) and the ONF Contributors
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.