Add tox.ini for flake8 config

Signed-off-by: Byron Ruth <b@devel.io>
Implement neo4j.Client class, fix purge method

The Client class simplifies persisting a "connection" to Neo4j for a
particular URI.

Signed-off-by: Byron Ruth <b@devel.io>
Implement APIs for manipulating resources and components

All queries have been moved to the origins.graph.queries module.

All statements have been changed to used parameters to take advantage
of prepared queries in the database.

Signed-off-by: Byron Ruth <b@devel.io>