Fixed JP_PREFECTURES to conform to ISO 3166-2:JP.

The JP_PREFECTURES does not conform to [ISO 3166-2:JP](http://en.wikipedia.org/wiki/ISO_3166-2:JP).

I fixed these points:

- Wrong order of prefectures.
- First elements of this, to code of the prefecture.

And, I left the old version of JP_PREFECTURES to be more compatible.

Thanks to the @tokibito for the reporting this problem to me.