implemented challenge1 according to task requriments:
 - on cart_item implemented methods: getPriceWithVat,getPriceWithoutVat, getVatAmount, getVat
 - on cart_driver implemented getTotalPriceWithVat, getTotalPriceWithoutVat, getTotalVatAmount
 - updated test view and ids controler to shows totals and price details
 - updated config to include default price, currency and currency format
 - updated item_cart forge and its config to use prices.