[WIP] BDD: Update structure for the inheritance fix

This belongs to a inheritance fix that involve:
- [ ] ezsystems/BehatBundle (PR comming)
- [ ] ezsystems/ezpublish-community (PR comming)
- [ ] ezsystems/ezpublish-kernel (EzPublishLegacyBundle and EzPublishRestBundle) (PR comming)
- [ ] ezsystems/DemoBundle (this PR)

Todo:
- [ ] move everything into an BddTest folder (so that the Feature and Context folder be on the same level)
- [ ] Update class names