configure-generated Makefiles don't include -Wall and a few issues had crept into the code.
tested at all yet, but it doesn't seem to have broken anything so it should be safe. See the README in the base package for docs.
PistonEngine class has grown an "Engine" superclass. Some other stuff moved around too, and I cleaned up some property naming while I was in there. This hasn't been tested very thorougly, hopefully I didn't break anything.