Fixed footer bar modernization and widget fixes

【Contents of fix】
■Updated the fixed footer bar for smartphones.
■Fixes to resolve widget errors in PHP7 environment.
■Changed the search URL of the widget “Google Custom Search” to https.

The following files have been modified for this update.
【Corrected files】
admin/theme-options.php
css/footer-bar.css
css/responsive.css
footer-bar.php
footer.php
functions/head.php
functions/seo.php
js/footer-bar.js
languages/ja.mo
languages/ja.po
style.css
widget/google_search.php
【Added files】
img/common/facebook.png
img/common/line.png
img/common/twitter.png
js/footer-bar2.js

For details, please see the download site for purchasers of MONOLITH (tcd042).