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/tox.ini b/tox.ini
index 92ae862..4bfe954 100755
--- a/tox.ini
+++ b/tox.ini
@@ -1,4 +1,4 @@
-; Copyright 2019-2023 Open Networking Foundation (ONF) and the ONF Contributors
+; Copyright 2019-present Open Networking Foundation
 ;
 ; Licensed under the Apache License, Version 2.0 (the "License");
 ; you may not use this file except in compliance with the License.
@@ -13,7 +13,7 @@
 ; limitations under the License.
 
 [tox]
-envlist = py27,py35,py36,py37,py38,3.10.6
+envlist = py27,py35,py36,py37,py38,3.9,3.10.6
 skip_missing_interpreters = true
 
 [testenv]