discodop parser: make --batch default, --simple for bitpar-like interface

- remove --batch option and make it default, replaced with --simple to
  get the bitpar-like interface.
- remove -z option, one sentence per line is default, bitpar format of
  one token per line is now the -x option.
- add example to docs of tokenizing a text with ucto and using 'discodop
  parser' on a text.