Fix issues on Prestashop website

Some issues to fix on our Prestashop website:
- Responsive product columns and other pages
- Forced one/same size for product thumbnails
- Add unclickable button on product page for coming soon items (cannot be added to cart yet)
- Add Q&A portion in product pages (like on Amazon)
- Extend whole width usage
- Add a carousel on homepage for testimonials
- Add a "highlights" section in the products page (with images and texts)
- and other minor css styling / positioning issues