BigDecimalField - support auto repeat on mouse press

Not sure you will be interested in this change. But.. What this change accomplishes is supports is adding support for auto repeat of the up/down arrow action of the BigDecimal field. Holding the mouse button down on the up arrow will increment the field repeatedly on a timer until the mouse is released. Holding the mouse button down on the down arrow will decrement the field repeatedly on a timer until the mouse is released. This behavior is helpful when the user wants to increment/decrement the value in the field quickly. Also, it makes the mouse actions a bit more consistent with the keyboard, as the up/down arrows on the keyboard exhibit the same behavior.