ogg2mp3

NOW

- need more checks:
    o check write permission to output dir
    o file and header integrety of the created mp3 must be checked

LATER

- add CL options to override inherited settings, so that one can
  take a 160 kbps ogg and get a 128 kbps mp3 or downsample the mp3
- get rid of ogginfo parsing:
    o as soon as Ogg::Vorbis::Header::PurePerl becomes usable and
      makes it into cooker

