scm_layer_impl
==============

Implement SCM's word layer.  Has three inputs: net_input, for inputs subject
to normalization and "power law" transformation, "frequency\_bias" for the
biasing input of frequency, and "inhibitory" for inhibitory inputs not
subject to normalization/"power law".  Two connections are needed from a standard spatial
layer if the standard separation into facilitation (shunted) and inhibition
(not shunted) is desired.

net\_input is divided by (length+2) and subject to a power law with `power`,
multiplied by `inweight` and then the inhibitory input added.  Then shunting
applies.  If `decay_delay` has passed since the last reset event, then
`decay` is applied to units whose activity is less than `cutoff`.

Parameters
==========

	parameter	default_value
	decay		0
	decay_delay	0
	rate		1
	cutoff		1
	power		1
	inweight	1
	max_act		0
	min_act		1