Feature/Auto date format

[elkrieg]

+fix of previos issue and unit tests

[Pitterling]

I'm going to merge. Well done for first shoot. I'm going to create a new issue to address open topics:

• several matches (mm/dd vs dd/mm) should fallback to "askDate"
• no match should also fallback to "askDate"
• determineDateFormat should be a own class

[Pitterling]

fixes #41