Refactoring tests to make them more robust

Fixed typo in feature description.
Merged two background steps since the last one did not have any actions
that could be done manually.
Removed assertions from a "given" (login) step. We already extensively
test logging in. If this extension needs login tests, they should go to
a separate feature file.
Moved methods from steps file to page file, following page object
pattern.

Change-Id: Ic5250970362718f5ed887c9ac8fd56948724b210
Merge "Refactoring tests to make them more robust"