Bug 12840: The budgeted cost and the total are automatically calculated

Bug 12840: The budgeted cost and the total are automatically calculated

Both of these 2 values should not be modified by the user.
Since these values depend on the discount and the quantity.

Test plan:
Verify you cannot modify the budgeted cost and the total price on
creating/modifying an order.

Signed-off-by: Paola Rossi <paola.rossi@cineca.it>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>