Reinstantiated node.activation to its former glory
Moved test for existence of world from general node function to the node function of the Actor
Requesting activation from a node no longer computes that activation (side effect)
Default node function calculates activation from slots, and calls gate functions with node activation
Setting node activation to gen
As node.activation is no longer a function of gate
activations, redraw checking has to be performed
on gate activation to catch all redraw conditions