Fixes #7

- Different way of dealing with the existing sentences and words so as to ensure that they will be kept if they encapsulate the boundaries found by the lexers;
- The prosody problem is fixed by distributing the sentences over an upper level than before (when it is forbidden to create a sentence where the lexer wants it to be).
- Removed prodnotes from the list of 'special-sentences' (not part of issue #7)