Behat 3 upgrade

Updating to behat 3

Changes:
- [x] Update from RegEx to Turnip
- [x] Convert from SubContexts to Traits
- [x] Drop sentences interfaces
- [x] Separate context of ObjectContext from implementation
    - context sentences: BehatBundle/Context/Object/<object>.php
    - implementation: BehatBundle/ObjectManagers/<object>.php
- [x] refactor structure
- [x] Add/clear file headers and file/class explanations
- [x] pass on that PR (https://github.com/ezsystems/ezpublish-community/pull/182)