Fixed multiple bugs

【Contents of fix】
■Fixed a bug where the ranking text color of the widget “Popular Articles List (tcd version)” could not be changed.
■Fixed a bug where the parent category of the recipe category could not be selected on the article edit screen.
■Fixed a bug in which breadcrumbs were not displayed correctly when there were no child categories in the recipe category.
■Changed the welcome message displayed on the top page so that different contents can be displayed for “logged in users” and “non-logged in users”.

【Modified file】
admin/css/my_admin.css
admin/inc/front_page.php
functions/head.php
header.php
languages/ja.mo
languages/ja.po
single-recipe.php
style.css
template-parts/breadcrumb.php