Add option selectTopping in selectLayerPage
Add selectToppingPage functionality

- UI for selectTopping was updated
- selectToppingsPage has a button for checkout
Refactor checkoutPage

- Bug fix: after a checkout the checkoutPage is not shown
- Change viewmodel name in the checkoutPage
Add checkout button to allaCartePage

- To keep consistency with selectToppingsPage, allaCartePage has a
  checkout button.
- Updated unit tests for allaCartePage
Use NavigationService instead of window location

- All pages use now the Navigation service
- Unit tests were updated
Merge pull request #15 from CHECK24/goCrazySelectTopping

Go crazy select topping