Remove version number from setup.cfg

pbr looks at the git tag for the version, so we do not
want a hard-coded value in the setup.cfg

pbr handles dev tagging automatically, so don't do
that via setup.cfg

pbr recursively finds packages, so we do not need to
list them explicitly in setup.cfg

Change-Id: I59a3e9d789c97f2cb9b6c487c553127af5a36b9f