Makefile library merge with onf-make and voltha-lib-go

makefiles/
----------
  o Import standalone makefile directories to checkin smaller parts of a mega patch.
  o Build out directory hierarchy by topic and feature.

makefiles/lint/yaml/
--------------------
  o Pull in logic evolved in repo:voltha-lib-go.
  o Refactoring: support special snowflake targets by repository.
  o ci-management and voltha-lib-go use distinct yamllint.conf files.
  o Separate until there is time to review and consolidate.
  o Added deps for on-demand local install of yamllint.
    - requirements.txt could be used but every build would incur overhead.

Makefile
--------
  o Use latest syntax from repo:onf-make.
  o No need to set path variables, makefiles/include.mk can infer them.
  o Added a help target to explicitly display targets and suggestions.
  o Logic is bundled in libraries and use of 'make help' is not well known.

Change-Id: Id8eba6f914a7bfe9a31637901bd8fb78a387e0c2
diff --git a/makefiles/git/include.mk b/makefiles/git/include.mk
index 9125178..42f2a47 100644
--- a/makefiles/git/include.mk
+++ b/makefiles/git/include.mk
@@ -20,17 +20,24 @@
 
 $(if $(DEBUG),$(warning ENTER))
 
+ifdef USE-ONF-GIT-MK
+  mk-include--onf-git := seen
+endif
+
+ifndef mk-include--onf-git
+
 ##--------------------##
 ##---]  INCLUDES  [---##
 ##--------------------##
-include $(MAKEDIR)/git/help.mk
-include $(MAKEDIR)/git/required.mk
+include $(ONF_MAKEDIR)/git/help.mk
+include $(ONF_MAKEDIR)/git/required.mk
 
-ifdef USE_ONF_GIT_MK
-  # Dynamic loading when targets are requested by name
-  include $(ONF_MAKE)/git/submodules.mk
-endif
+## Special snowflake: per-repository logic loader
+-include $(ONF_MAKEDIR)/git/byrepo/$(--repo-name--).mk
+
+# Dynamic loading when targets are requested by name
+include $(ONF_MAKEDIR)/git/submodules.mk
+
+endif # mk-include--onf-git
 
 # [EOF]
-
-