VOL-4917 - voltha-go build and test problems.

  o Update copyright notice.
  o Added a few common makefile libraries.
  o Added todo.mk to document a few future-fix items.
  o Added versions.mk used to display build tools and versions.
  o Added comments and banners to delimit logic and identify log output.
  o Fixed coverage target, git test -coverprofile requires a disk file.
  o Strange: 'go mod vendor' will remove vendor/ but the directory is
    under revision control.  [TODO] Delete or checkout from a central repo.
  o Split long lines with line continuation at shell pipe.
  o Replace inlined rm -rf calls with make builtin $(RM) -r
  o Refacor test log names into macros to shorten logic line length.

  o Update copyright notice.
  o Inline --no-cache with apk calls, networking problems surfaced while
    running "make build/test" while disconnected from the VPN.
  o Copy stub go-test-coverage.out file to the docker image, go test
    -coverprofile was failing w/o a file on disk.
  o Testing reported a "could not create cpu profile" error.  Create a pull
    request for feedback to see if this is a lingering coverage problem or
    my laptop cpu is unknown and contributing.

Change-Id: I84724682cfd9dbcd08990cef382338f005261184
diff --git a/VERSION b/VERSION
index 9cec716..23887f6 100644
@@ -1 +1 @@