[WIP] Added Orm testing

| Q             | A
| ------------- | ---
| Bug fix?      | probably
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #142
| License       | MIT
| Doc PR        | -

This is a work in progress. Currently, only mocked unit tests are done.

## Todo

 - [x] Add ORM DbManager to symfony-cmf/Testing
 - [x] Add Functional tests

## Requires

This PR requires these PRs to merge first:

 - [x] symfony-cmf/Testing#13