[WIP] 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
- [ ] Add/clear file headers and file/class explanations
- [ ] pass on test PR
Getting an error on fillField
```
 Scenario: As administrator I can see restricted objects # vendor/ezsystems/demobundle/EzSystems/DemoBundle/Features/Content/site_map.feature:98
    Given I am logged as an "administrator"               # EzSystems\DemoBundle\Features\Context\ContentContext::iAmLoggedInAsAn()
      Method 'fillField' doesn't exist in 'EzSystems\DemoBundle\Features\Context\ContentContext' (Exception)
```