Fixed multiple bugs / Added new features

【Contents of the fix】
■Fixed a bug that the global menu on the login screen does not display properly when using Welcart e-Commerce (version 1.9.23).
■Fixed the error display on My Page when using the WelcartPay, Lumise, and Zeus payment modules.
■Implemented the custom script function.

The following files have been modified for this update.
【Fixed files】
admin/inc/basic.php
admin/theme-options.php
functions/head.php
functions/welcart.php
header.php
languages/ja.mo
languages/ja.po
style.css
wc_templates/member/wc_member_page.php