Feature request: Ability to reverse the up/down buttons on NumericInput

[brainbarker]

I'm trying to use NumericInput to allow users to page through a long document. For paging, the natural order of the up/down buttons is the opposite of the way the control works (up button should be previous page, down button should be next page). I tried to achieve this by using a negative stepSize, but that causes an error.

Edit:
This change should also apply to using the up/down arrow keys when focus is on the value input box. Up arrow should decrement, down arrow should increment.