Better handling of REST methods, added cart API endpoints
Minor CSS changes
Changed button style to use CSS subclasses

Now btn is the main class with btn-submit, btn-cancel and btn-info for
different colourings
Changed button style
Added the ability to show an item detail
Ability to add item to cart
Added class attribute to dismiss button
Nav bar changes, added session control methods
Updates method name to show item detail
Added overlay, item and cart files (CSS/JS)
Updated button style to new naming structure
Added JS/CSS lib to show the user's cart