Feature: Universal Language Selector Accept-Language, Scenario: Accept-Language is German

The commit has two ugly hacks:
1) When the scenario code is executed, the browser is already opened,
but setting browser language has to be done before the browser is
opened. Ugly hack: close the existing browser and open a new one.
2) Base URL is hardcoded into RandomTranslateWikiPage. Will refactor it
soon. I promise.

Change-Id: I7e08daf82cdad0fe204e2198c2598335b384884a