bug_4831: Use unitprice (actual cost) when totalling spent amounts for "All available...

bug_4831: Use unitprice (actual cost) when totalling spent amounts for "All available funds", as in "Already received"

Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>
To test:
- add new fund for an active budget
- order item, price 8.00
- check funds page and acq home: committed amount should be 8.00
- receive item, enter actual price 10.00
- check funds page and acq home: spent amount should be 10.00

Signed-off-by: Ian Walls <ian.walls@bywatersolutions.com>
Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>