Quantity in transactions

It would be cool to see the quantity in the single transaction (by default: 1), and automatic recalculation of subtotal value of the transaction. Following by that - provide the setting to control whether we want to see the quantity in the transaction tables or hide.

For example the expense is -10, quantity is 2, then whole transaction should be shown as -20, but both of those values should be kept.

Useful when user wants to put several items (ie 4x milk) or weighted values (0,45kg for apples), but the unit isn't required.