This reverts commit 0bc61d3c21.
The volume mapping does not match what the original is doing. In the
case of this bug, a volume of 127 for the fountain sound would be
mapped to 2/255 when standing right in front of it, which is too quiet.
Also, rename the graphics 'Effect' class in order to avoid naming clashes (and/or coder
confusion) with the newly named ScriptingEffect class.
Lastly, add some documentation for the classes for further clarity.