sambacc: add initial support for checking JSON schema of config

container: container build based on new home repo

Support git / github by default in the build & test container.  Still allow
basic hg functions as I'm going to keep using hg (as a wrapper over git).

readme: make github the canonical home for sambacc (sigh)

I am surrounded by git lovers! ;-)

sambacc: drop bad/hacky attempt at validation

tests: test OSError handling via pytest monkeypatching

This works even if the test is being run in a container as uid 0

tests: dont run chmod based test as root, it doesn't work

sambacc: allow tests to override _open when testing config module

tests: add test for explicitly defined groups

sambacc: fix processing of explicitly defined groups

tests: add test coverage for GroupEntry fields

sambacc: add missing entry_num field to GroupEntry

tests: add test coverage for UserEntry fields

tests: check errors in GroupEntry record input

tests: check errors in UserEntry record input

tests: check error handling of read_config_files

tests: check that adding duplicate users/groups has no impact on output

container: run yum clean all too

container: support running passdb tests in the container env

This adds a bunch of integration stuff to allow tox+py.test to actually
run the passdb tests, as it needs both the samba libs and the ability
to add matching entries to an "etc passwd" file before any interesting
stuff happens.

tox: allow verbose py.test output and pass env vars

tests: add test functions for passdb loader

These tests require system level stuff to be set up. So its probably
best to only run these in the container test env.