Added support for multiple tag lines for features and scenarios

[Jack12816]

- What is it good for

This PR ships a parser extension to allow multiple lines of tags before features and scenarios. With this change in place its possible to have:

@test
@wip
Feature Multiple Tag Lines

  @pending
  @tags @even-more-tags
  Scenario Parses multiple tag lines correctly
    Given ..

- What I did

I added a new ScenarioTags nonterminal next to the present FeatureTags one. And used it on the Scenario nonterminal. And the FeatureTags nonterminal was enhanced to allow newlines in between, too. Last but not least some specs were added to validate the change.

- A picture of a cute animal (not mandatory but encouraged)