Automatically update products fields (total) when editing order items (price, qty)

[AndreiMaz]

Continuation of task (https://github.com/nopSolutions/nopCommerce/issues/8). Right now we update order totals. Product quantity will automatically calculate the total of the product itself. When I manually add the correct price for the product totals then it also has the correct order totals.

1. When a value of "Price (incl tax)" or "Quantity" is changed and input focus is changed, then we should automatically pre-set (using javascript) the product "Total (incl tax) value
2. Do the same for "excl tax" values
3. Let's get a valid "order total" values using AJAX because it could depends on some complex price rules
4. Make it configurableso it can be disabled (if something goes wrong)

Source: http://www.nopcommerce.com/boards/t/46077/order-price-doesnt-update-when-manually-add-a-product-to-order-from-admin.aspx#182880