[WIP] Added Orm support

This is just an exact copy of #12, only difference is it uses another base (one that's in this repository). This enables testing this with the RoutingBundle.

From #12:

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | symfony-cmf/symfony-cmf-docs#230

This PR adds support for ORM. It contains:

- very simple DbManager
- bash file for setting up ORM environment
- support for phpcr (default) and orm environments.

This means that instructions will change for bundles which support the ORM. I'll update the docs acordingly.
Also, a bundle needs to take care of registering correct mappings and requiring the orm package. The first one is because it's bundle specific and including it here will make this too specific. The second is because not all bundles needs ORM tests, including it in this require section will lead to slower tests.

It's a WIP because I want to fully test it with the RoutingBundle first