do not multiply the output of attr_output_fn with the model's output,
as this is neither intuitive nor flexible
instead, only sum over the attr_output_fn output to compute the
batch-wise scores
in share/example/feed_forward.py: specify an attr_output function instead
of a one-hot tensor, which uses only the output of the true label
index, thus retaining the previous behavior and demonstration how to
use the output function
in docs/source/how-to/use-attributors.rst: use a lambda expression for
the occlusion attributor to demonstrate how to use score only for a
certain index with the new interface