Fixed multiple bugs / WP5.0 compatible

【Contents of fixes】
■Support for WordPress 5.0 (Gutenberg)
■Fixed the bug that the magnifying glass icon is displayed even if the search window in the header is hidden.
■Adjusted the number of articles displayed in Top Page > Main Contents > Blog Contents.
 ※There was a case where the set number of articles were not displayed, so it has been fixed. We apologize for the inconvenience, but we would appreciate it if you could review the settings once again just to be sure.
■Fixed a bug in which style settings were not properly reflected when there was a hidden block in the main content of the top page.
■Fixed a bug that the date and time of events are treated as UTC regardless of the time zone setting.
■Fixed the bug that meta description is not output.
■Fixed a bug that meta title and meta description could not be changed in quick edit.
■Fixed PHP7 support.
■Added some wording to theme options.
■【IE】Fixed a bug that the aspect ratio of the image is broken when the header content is set to post slider type 2 or 3.
 ※However, in IE, the image will be enlarged (or reduced) at the top-left corner of the image.

The following are the files that have been modified for this update.
【Corrected files】
admin/inc/basic.php
archive-event.php
front-page.php
header.php
inc/admin_column.php
inc/event.php
inc/head.php
inc/seo.php
inc/widgets/custom-menu.php
languages/ja.mo
languages/ja.po
pagebuilder/assets/admin/css/admin.css
pagebuilder/assets/admin/js/admin.js
pagebuilder/assets/admin/js/googlemap.js
pagebuilder/assets/css/googlemap.css
pagebuilder/assets/css/pagebuilder.css
pagebuilder/assets/css/slider.css
pagebuilder/assets/js/googlemap.js
pagebuilder/modules/catchcopy.php
pagebuilder/modules/googlemap.php
pagebuilder/modules/headline.php
pagebuilder/modules/image.php
pagebuilder/modules/simple_table.php
pagebuilder/modules/slider.php
pagebuilder/modules/tab.php
pagebuilder/pagebuilder.php
past-event.php
single-event.php
style.css
taxonomy-event_tag.php
template-parts/hero.php