Frontend updates & general bug fixes

Fixed the shop to successfully show an array of items when you selected
their category.

Also implemented the mailing system on the frontend.

Added the mail class to the frontend index.php so it can be used for
register and contact.

Fixed the contact page so it should be functional now.

Small bug fixes overall.

Changed database/config/db.config.php to database in .gitignore so the
entire folder is ignored.