Remove disabled tests from Euro test
Remove disabled test from simple test
Remove another disabled test
Use more diacritics in the euro accented character test
Add a polish character to the accented character test
Add another test method, format the GitChangeSetTest
Return unknown user rather than throwing exception in GitChangeSet

Refer to [JENKINS-16737] and [JENKINS-10434] for two cases where a
GitChangeSet cannot find an author and throws a RuntimeException when
it would be much better to report an unknown user and allow execution
to continue.