doc: Italian translations

[Federico Vaga]

Ciao Jon,

here again the doc-guide translated in Italian and the Italian
skeleton. This set of patches is a bit different than the privious
one. Main differences:

- I moved out translations from the main index
- I fixed the Italian translation for the kernel-doc.rst file
  because I noticed that you restructured it and simplify
  (my fault I did not check it before)
- I added my self as MAINTAINER of the Italian translation effort