Sets the given buttons's label sprite.
PRVirconBtnSetLabel(btnId, sprite, xOffsetX, yOffset, scale, shouldScaleWhenSel, rotation) 
The button ID.
The sprite to use for the button's label.
The x-offset of the label sprite from the center of the button.
The y-offset of the label sprite from the center of the button.
The scale size to apply to the label sprite with 1 being normal size.
true or false indicating if the label should scale when the button is pressed. Useful for when the label is positioned outside of the button's body.
The angle at which to draw the label sprite.
n/a