doc: update po ja

related to 328b360e5a103ec31cce5942f8a97464b7dd3fbf and cfaf7aa1cda483ca9a1109b64b1b03ff3bd56c27
update file list

`make update-files`
related to #186
Merge pull request #194 from cosmo0920/po-translate-ja

doc: update ja Po and file lists

Patch by cosmo0920. Thanks!!!