Multiple bug fixes

【Contents of fixes】
■Changed Facebook OGP setting from old specification (fb:admins) to new specification (fb:app_id).
※Please refer to the following article about how to get “fb:app_id” (application ID).
 How to get the fb:app ID required for Facebook OGP settings
■Fixed a bug in which the title of the 404 page was not displayed properly when the date was hidden in the “Display settings for each item” section.
■Changed the specification so that related articles can be displayed on the article detail page.
■Social Button Type 5 (Official Button) “Facebook Like Button” specification change support
■Removed “Google+” from the social button settings.
■【Mac】Fixed a bug in which the thickness of Japanese and European text may be displayed differently when using some fonts.

The following are the files that have been fixed in this update.

【Modified file】
404.php
admin/theme-options.php
comments.php
functions/custom_page_link.php
functions/ogp.php
functions/seo.php
functions/update_notifier.php
japanese.css
languages/ja.mo
languages/ja.po
sns_btn_btm.php
sns_btn_top.php
style.css