feat (ShopService): new service to get the ApiRoot resource

For testing purpose a shop.json is included. It will be replaced with the actual call to the backend server.
refactor(MainView): move header and footer to index.html

header and footer is shared in all the views
feat(CustomerList): add an empty customer list route

Create Controller, View and initial tests to start with the Customer List funtionality
feat(Nav): add NavCtrl to manage the menu

Allow to dinamically add item to the menu and change the active one when navigating.