List e2e Tests: refactor navigation methods

[sgobotta]

The navigateToNextPage, navigateToFirstPage seems to be repeated in every test for the List views.

My first thought is to refactor those 2 functions to the tests/e2e/lib/helpers.js directory.

• Check if another module holds better the functions refactor
• Refactor the articles List e2e test.
• Refactor the magazines List e2e test
• Refactor the authors List e2e test
• Check all the tests pass