Add boilerplate for zettel 10
Work on zettel 10
Finish problem 1
All the tasks.

But looking throught it once more is suggested.
Finish zettel 10
Add secondary constructor to Artikel, remove nulls

The nulls were in TwitterAccount, rather than specifying them explicity I've set
the field initialization to _, which defaults to null for these objects.

Rather than writing a second constructor for Artikel, I'd originally rewritten
the class. Now I've included a second constructor that calls the first
constructor.
Merge branch 'test-benennung' into danielZettel10

Conflicts:
	docs/zettel/zettel10.pdf
	src/zettel10.scala