Simplify API design.

Removes the "namespace" and the *user* behavior I tried to impose into
the API (I don't know why) since it is utterly unecessary for the
objectives of the project.

PS: maybe an hierarquical API with an authentication API could be used
to create the very same behavior.
PPS: maybe just a proxy with HTTP digest authentication providing the
very same thing.
PPPS: above "PS"es just proves the "utterly unecessary" point.
Add bootstrap, cli, db connection and Composer.

- Add dependencies on composer.
  - Doctrine\Migrations
  - Symfony\Console
  - PHPUnit
  - Behat
  - Respect\*
  - Monolog
- Configurations available:
  - Command Line Interface (Database migrations)
  - Database
  - Environment (PHP configuration, database configuration)
Add first database version.
Create *bin* directory.x