[Discussion only] First attempt on a more imperative approach

**do not merge** - this commit will be added on a PR with the implementation

Changes done from the original idea (original idea at [ezsystems/BehatBundle/Features/*](https://github.com/ezsystems/BehatBundle/tree/master/Features)):
- move from a strait declarative way to a declarative/imperative way
- update feature description to match the actual User Stories
- merge the anonymous/administrator users to same feature file since the user (actor) is a developer

Should the errors be made on declarative or imperative way?