Adding objects to a large position is slow

[jsoa]

If a position contains alot of items, adding an item to it is slow. It becomes even slower with more items in the position. This is when we are using add_object, which does some checking and re-ordering on the fly. While having over 500 items in a position is rare, the case where a position is used as a ban or white of users for example, the list may get large. In this case the order does not really matter and the re-order can be neglected

Suggested changes:

• Add a manager method that just appends to the list taking the next order #
• Add a bulk add object method that accepts a list of objects and uses the the list order.