Add ja localization to release/1.6.1 branch

[hkurosawa]

Just created another PR for release/1.6.1 to add Japanese localization.
this should be the base of localization for another languages.

The following PR can be closed if this works. thanks.
#123

[fikovnik]

Amazing! Thanks a lot.

One thing - the MainMenu.xib is not localized, is that correct?

[fikovnik]

I did a little merge and pushed it back. There is one more string missing:

"AUTHORIZATION_INFORMATIVE_TEXT_10_8" = "ShiftIt needs to be authorized to use an Accessibility Service in order to be able to move and resize application windows.\n\nPlease \"Enable access for assistive devices\" in the System Preferences > Universal Access and then restart ShiftIt.";

Thanks!

[hkurosawa]

MainMenu.xib menu item strings (other than the bottommost section) seems to have no need to be localized because it will be substituted by the code within initializeActions_ method in ShiftItAppDelegate class which is already localized by Localizable.strings.

As for "AUTHORIZATION_INFORMATIVE_TEXT_10_8", I'm sorry I missed it, will soon prepare another Pull Request for that fix. Thanks.