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/shell.mk b/makefiles/lint/shell.mk
index 9f8cd58..da92921 100644
--- a/makefiles/lint/shell.mk
+++ b/makefiles/lint/shell.mk
@@ -23,7 +23,7 @@
 
 lint-shell:
 	shellcheck --version
-	find . \( -name 'staging' -o -name 'vst_venv' -o -name 'vendor' \) -prune \
+	find . \( -name 'staging' -o -name 'vst_venv' \) -prune \
 	    -o -name '*.sh' ! -name 'activate.sh' -print0 \
 	| xargs -0 -n1 shellcheck