VOL-1449 Modify build environment to use pyvoltha

Depending on if LOCAL_PYVOLTHA is set use a build of
the library from the nearby source tree, for both
virtualenv and docker image builds.  By default
requirements.txt uses the pip hosted dev build, which
may not be new enough for iterative development

Also by setting PYVOLTHA_BASE_IMAGE use a docker image produced
by pyvoltha as the base image.

Change-Id: Ibf7218b92450f92d6a3f1c9d837be46fcc3a84db
11 files changed
tree: 664130ab737d2d4a609c3469a7a2f6b76932e36f
  1. .gitignore
  2. VERSION
  3. python/