At end of test: also make screenshot

[bruderol]

As a user I also want to see a last screenshot after the test has finished (maybe the last action was not a click or a get request or the test even failed).

• also make screenshot on test finished
• only store if there is a visual change compared to previous screenshot
• store failure status on the last step if this screenshot happens on failure 8in this case we should maybe store in any case together with the stacktrace, or do we only store this on the scenario?)