Snippets from non english scenarios

Generate snippets with ``@Given``, ``@Then``, ``@When`` from non english scenarios. 
After added keyword type to ``StepNode`` in __Gherkin 4.2-dev__ (see Behat/Gherkin#69) .

Also snippets with keyword types ``And``, ``But`` are normalized to ``Given``, ``When``, or ``Then``. 
Rule: Get type from previous step if exists, else set to ``Given``.

Fixes #277, #317