More efficient hauling

[zyklame]

Currently i have the problem watever i do the hauling is inefficient.
There are two scenarios:

- If i have no haulers the colonist run out for evry job they do and waste time.
- If i have haulers they fill the nearly full stockpiles first and don't fill the others, because in the most cases a few items are used by the time the hauler deliver and he run ageain to fill the same stockpile with only 3 to 5 items.

It would be nice wenn the colonist allways try to fill full stacks first. For example they only refill the storage when it fall under a critical ammount.