effects,fastscramble,objectchange: license.
Major change: separate the notion of a TwistyObject and its Node. Now,
1) the Node stays when we change objects (this makes transitions faster)2) it's possible to just create an Object without adding it to the Screen (now app needs to explicitly create the Node and add it to its Screen itself)
Relax objectlib's requirements: it can be displayed not only on top of a DistortedScreen, but any DistortedFramebuffer.
Move yet more code to objectlib.