new binarization options & other fixes

- when deciding whether to normalize a bitpar grammar, don't look at
  lexicon because that may contain smoothed weights despite needing
  normalization.
- postprocess trees when using 'discodop parser' command with a model.
- treetransforms:
  - some new binarization options
  - remove pospa option, use treebanktransforms instead.
  - move around functions
- other fixes