Updated holiday file for Italy (Italian)

- add "religious" when appropriate to many "public" days
- add "commemorative" when appropriate to public and cultural days
- split Ascension date to the proper one vs the one mostly celebrated
  in Italy (see bug#329285)
- split "Festa della Repubblica" which was not "public" (commemorative
  only) before 2001
- move "Festa dell'Unità nazionale" to commemorative (end of WWI)

BUG: 336683