Solidity Natspec multiline /** .. */ comments

- Natspec now works with `/** ... */` type of comments.
- Some work on better formatting of the extracted text, especially on the multiline comments case
- Adding CR ('\r') as whitespace in the scanner
- Some tests
What happens if some comment line does not start with a `*`?
What if some line is empty?
What if there are other non-whitespace characters before the first `*`?