summate_connection_impl
=======================

Sum the activation on the source output, multiply by `excitation` and use
this as a multiplier on the (localist) answer pattern to produce the target
input.

Parameters
----------

	parameter	default_value
	excitation	0

answer_pattern
--------------

	some_sumc answer_pattern apat

Copy the value of the answer pattern `apat` to the lookup table for
determining the output.