Get rid of quadratic active-checking (and the deepcopy of self.locations on every reset()) in Spiral plugin.
Represent Scene's list of all pixel locations as a numpy array instead of a
list. This speeds up plugins and presets that use the location list (as many
convert it to a numpy array first). In the case of Spiral presets, the draw time
drops from 40ms on average to 2ms! Transitions are much faster now.
Don't get all pixel locations in the draw method of Spiral. Do it in reset() instead.
Forgot numpy imports.