Add SQLalchemy database model

As a step towards continuous deployment and having a pecan/WSME REST
interface, split the database out into SQLalchemy-based model using
Alembic for migrations. To support that, also pull in oslo.db and use
oslo.config for config files.

Change-Id: I33a1e72700be14e28255aaa52faed70c4686a3ec
Introducing basic REST API

This is initial commit adding pecan/wsme framework.
Example operations are:
* GET /v1/project_groups
* GET /v1/project_groups/<group_name>

* GET /v1/projects
* GET /v1/projects/<project_name>

* GET /v1/teams
* GET /v1/teams/<team_name>
* POST /v1/teams

* GET /v1/users
* GET /v1/users/<username>
* POST /v1/users
* PUT /v1/users/<username>

Change-Id: Ibace8cf7dd5bb933b0d2484b1d57b79bb8441a28