* add the `voxpopuli` recipe
- this is the data preparation
- there is no ASR training and no results
* update the PR#1374 (feedback from @csukuangfj)
- fixing .py headers and docstrings
- removing BUT specific parts of `prepare.sh`
- adding assert `num_jobs >= num_workers` to `compute_fbank.py`
- narrowing list of languages
(let's limit to ASR sets with transcripts for now)
- added links to `README.md`
- extending `text_from_manifest.py`
