[VOL-5194] - Update repo to use library makefiles.

https://gerrit.opencord.org/plugins/gitiles/onf-make
----------------------------------------------------
This patch will begin replacing the makefiles/ directory (target and logic
duplication) with centrally maintained library makefiles.  repo:onf-make
has been added as a git-submodule.

Simplest patch given the amount of changes needed.
It will only alter where duplicate target logic is included from.

.gitmodules
makefiles/onf-lib
-----------------
  o Checkout repo:onf-make as a submodule of voltha-docs.

makefiles/local/include.mk
--------------------------
  o Add a directory for per-repository makefile targets and overrides.

config.mk
makefiles/config.mk
-------------------
  o Relocate config.mk to avoid cluttering the repository root.

Makefile
--------
 o Replace high level imports with a single library makefile include.

makefiles-orig/virtualenv.mk
----------------------------
  o Help target cleanups, edits will migrate into repo:onf-make
    prior to removal of the local virtualenv.mk makefile.

makefiles/include.mk
--------------------
  o Added new install.mk include used to load onf-lib and local makefiles.
  o Staging: define onf-mk-lib as makefiles-orig/ for now.
  o Legacy makefile cleanup still needed before makefiles/local can be used

howto/index.rst
howto/nop.rst
---------------
  o Cosmetic edit to force a build/license check.
  o Last recheck attempt reported "No Builds Executed".

Depends-On: I7c83bd48d26510e79fd32f8bb97887cace67b55f
Depends-On: If75417c45363ee5c6a514fe9ebd4414ba8cf0cf7
Depends-On: I637d58f3e983b6cb1b7f08d19f16da925a579668

Change-Id: I8d7e53da91e52642726f1c8b997952765cbc1c23
Signed-off-by: Jan Klare <jan.klare@bisdn.de>
diff --git a/Makefile b/Makefile
index 99a5aeb..f99c809 100644
--- a/Makefile
+++ b/Makefile
@@ -26,8 +26,7 @@
 ##--------------------##
 ##---]  INCLUDES  [---##
 ##--------------------##
-include $(TOP)/config.mk#                # configure
-include $(TOP)/makefiles-orig/include.mk      # top level include
+include $(TOP)/makefiles/include.mk      # top level include
 
 # You can set these variables from the command line.
 SPHINXOPTS   ?=
@@ -89,7 +88,10 @@
 # coverage
 # linkcheck
 
+# -----------------------------------------------------------------------
 #  currently not enabled, should be added to lint target
+# [TODO] Create repo:onf-make/makefiles/lint/mdl
+# -----------------------------------------------------------------------
 LINT_STYLE ?= mdl_strict.rb
 md-lint: | $(OTHER_REPO_DOCS)
 	@echo "markdownlint(mdl) version: `mdl --version`"