Makefile edits to improve library lint target support.

Makefile
--------
  o Replace inlined includes with single $(MAKEDIR)/include.mk
  o virtualenv install w/dependencies handled by makefiles/virtualenv.mk
  o Use '&&' for command separation to improve error handling.
  o Added more target documentation.
  o Re-home doc8/rst syntax checking into makefiles/lint/doc8.mk.

howto/code/linting.rst
----------------------
  o Document supported lint targets on docs.voltha.org.

howto/release/index.rst
howto/release/post-release/
howto/release/vcs/
---------------------------
  o Document more release related activity (bugfix branch creation)

makefiles/consts.mk
-------------------
  o Define and use more library macros.

config.mk
---------
  o Per-repository library makefile configuration, disable linting.

makefiles/virtualenv.mk
-----------------------
  o Library virtualenv install with dependences.
  o Begin using a consistent install directory.
  o Ugh: repository (voltha-docs) submodules each install a full venv.
  o Install dependency drive based on existence of activate script.
  o Lint targets updated to use activate script as a dependency.
  o Update activate macro to run:  set -u && activate && set +u

makefiles/patches/include.mk
----------------------------
  o Update to use virtualenv.mk defined macros.

makefiles/lint/doc8.mk
makefiles/lint/python/flake8.mk
makefiles/lint/json.mk
makefiles/lint/python/pylint.mk
makefiles/lint/robot.mk
makefiles/lint/shell.mk
makefiles/lint/yaml.mk
-------------------------------
  o All library linting defines consistent targets and logic.
  o Support two library targets: lint-all and lint-modified.
  o Default to checking all available sources.
  o Linting can be disabled per-repository via {project}/config.mk

Change-Id: I7b7b5e523c867183d44244a0da21cfa3584e9a50
diff --git a/howto/release/post-release/gitreview.rst b/howto/release/post-release/gitreview.rst
new file mode 100644
index 0000000..7bebb82
--- /dev/null
+++ b/howto/release/post-release/gitreview.rst
@@ -0,0 +1,30 @@
+gitreview branch update
+-----------------------
+
+After a release has been created and repositories have been branched & tagged:
+
+- voltha-helm-charts
+- voltha-system-tests
+
+Update the .gitreview file on the voltha-x.y release branch so commits are
+directed to branch=voltha-x.y rather than the default voltha=master
+
+.. code-block::
+   :emphasize-lines: 6
+
+   [gerrit]
+   host=gerrit.opencord.org
+   port=29418
+   project=voltha-helm-charts.git
+   defaultremote=origin
+   defaultbranch=master
+
+.. code-block::
+   :emphasize-lines: 6
+
+   [gerrit]
+   host=gerrit.opencord.org
+   port=29418
+   project=voltha-helm-charts.git
+   defaultremote=origin
+   defaultbranch=voltha-2.11