Multiple bug fixes

【Contents of fixes】
■Fixed the display specification of “Next post, Previous post link” on the blog detail page.
■Corrected the display specification of the global menu grandchild menu item on the top page.
■Fixed the specification change of the social button type 5 (official button) “Facebook Like Button”.
■Removed “Google+” which is no longer available from the social button settings.

The following files have been modified for this update.

【Modified file】
admin/theme-options.php
css/responsive.css
sns-btn-btm.php
sns-btn-top.php
style.css