The fontset now depends on the language rather than the skin.

- Fontsets are declared in "boards/fontsets"
- Localizers choose their fontset in the .po-file
- Moved the font definitions from babyskin/gartoon to
  the "sans" fontset and made it the default fontset
Using skin fontsets now
Improved layout for level and score numbers.

- Centered everything and created enough space for levels > 9
- New common font definition "levelmenu"
Bugfix: Play the audio level number now works with level > 9