Major updates to both frontend and backend
Frontend: added shopping cart functionalities
Frontend: updates styles
Frontend: added shopping cart handler
Frontend: added related and specs tab to product page
Frontend: added information to footer
Frontend: updated footer information
Frontend: updated texts to localized texts
Frontend: updated shopping cart functions
Frontend: added refresh and delete button to shopping cart view
Frontend: added checkout page
Backend: fixed minor errors
Backend: fixed identity error
Backend: added informations
Backend: added reviews
Backend: added downloads
Backend: added filters
Backend: added options
Backend: added settings manager and system settings
Backend: added users