a few fixes ; use Vec<String> in Paragraph

- indent_str.clear() for crown and tagged modes when !second_done
  because we set a sane default the first time through but now
  we need to change it a bit

- make sure nLen is calculated correctly after we push_char(' ')
  when we find '.' at end of line.

- Paragraph now holds Vec<String> rather than Vec<FileLine>. We got
  the necessary info from the FileLine, no need to hold onto it longer