General clean-up after rename.
General clean-up after rename.

- Removing "graft google" from MANIFEST for umbrella
  package. It isn't needed since the umbrella package
  has no source
- Updating license year on copy-pasted namespace package
  __init__.py files. Done via:
  https://gist.github.com/dhermes/a0e88f891ffffc3ecea5c9bb2f13e4f5
- Removing unused HTML context from docs/conf.py
- Setting GH_OWNER AND GH_PROJECT_NAME (which together make the
  REPO_SLUG) manually in the docs update scripts. This way the
  env. variables don't need to be set in the Travis UI / CLI.
  Also updating tox.ini to stop passing those variables
  through
- Removing the root package from `verify_included_modules.py`
  since it no longer has any source
- Updated a docstring reference to a moved class in the
  Bigtable system test
- Removing redundant `GOOGLE_CLOUD_*` in `tox` system test
  `passenv` (already covered by `GOOGLE_*`)

googleapis/python-storage,googleapis/python-storage