Behat 3 upgrade

Upgrade to Behat 3

Biggest changes:
- [x] subcontexts to traits (need to change inheritances and interface implementations)
- [x] RegEx to Turnip (horray!)
- [x] Update the feature sentences to refelct better the actual actions
- [x] Refactor REST drivers
- [x] chained steps were dropped (workaround needed)
- [x] Refactor structure/namespaces

To do:
- [x] above changes into REST
- [x] above changes into Admin
- [x] above changes into Setup Wizard
- [x] pass on test PR (https://github.com/ezsystems/ezpublish-community/pull/182)

nitpick: missing method `public` visibility