Update Japanese translations.

Update Japanese translations.

* Fix some inconsistent translations.
* Translate some missing messages.
* Update Japanese phrasebook.

Merge-request: 1249
Reviewed-by: ossi
(cherry picked from commit 7eb590b5bb00e5cfb8e153938f55013eebe94880)

Conflicts:
	translations/assistant_ja.ts
	translations/designer_ja.ts
	translations/linguist_ja.ts
	translations/qt_help_ja.ts
	translations/qt_ja.ts
	translations/qtconfig_ja.ts

Change-Id: Ic392e479ac6ebc1556e8c625ed98c1ac169a4b83
Reviewed-on: http://codereview.qt-project.org/4616
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@nokia.com>