Add height setting to snow brush

[zachman42]

In the standard //snow command, there is a height option that defaults to the world height, which is an accurate representation of how the decoration engine in the game works. The brush, on the other hand, has the height strictly set to the diameter of the brush. This can lead to unusual clusters of snow in inaccurate areas, such as under trees or even indoors. This can be solved easily by adding a height parameter to the brush.