Added and revised Japanese translation

[knagasaki]

No description provided.

[ebeshero]

@martindholmes Would you take a look at this to review the translations? We also need to check with the conflict on the branch.

[martindholmes]

@ebeshero I'm not really competent to review the translations as such, of course, but I do look at the spreadsheet where the work is happening sometimes to see if there's anything doesn't seem right to me. I think the att.pointing conflict arises from the other work to add final periods to desc elements, affecting the French translation which comes right after the Japanese; the other one seems to be a whitespace change, possibly from the same work.

I do want to make a point of running another check for issue #2337 before the next release, so once this is merged, I'll do that.