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/consts.mk b/makefiles/consts.mk
index c96cb88..043ec65 100644
--- a/makefiles/consts.mk
+++ b/makefiles/consts.mk
@@ -1,6 +1,6 @@
 # -*- makefile -*-
 # -----------------------------------------------------------------------
-# Copyright 2022 Open Networking Foundation (ONF) and the ONF Contributors
+# 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.
@@ -13,18 +13,16 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-#
-# SPDX-FileCopyrightText: 2022 Open Networking Foundation (ONF) and the ONF Contributors
-# SPDX-License-Identifier: Apache-2.0
 # -----------------------------------------------------------------------
 
-null        :=#
-space       := $(null) $(null)
-dot         ?= .
+null         :=#
+space        :=$(null) $(null)
+dot          :=.
+HIDE         ?=@
 
-HIDE        ?= @
-SHELL       := bash -e -o pipefail
-
-env-clean   = /usr/bin/env --ignore-environment
+# use bash for pusdh/popd and quick failures.
+# virtual env(s) activate has undefined vars so no -u
+#   ^---+ verify this is still true
+export SHELL := bash -e -o pipefail
 
 # [EOF]