This allows us to exploid Java 8 streams and Java 5 for-each
loops. The returned Collections are usually unmodifiable. We decided
against returning Iterable because this would mean determining the
size in O(n) compared to Collection.size() which is often faster
(e.g. O(1)).
Change all \r\n into unix style newlines. Add missing newlines at the
end of a file and activate the newline checkstyle module, that enforces
'\n' as newline and a newline at the end of every file.