Cleaning up a bit.

The test works in isolation:

	BUSTED_OPTS='-p analog' make net

it fails to connect to the devices when not:

	make net
Unit test the reverse uncalibrated analog output by testing for linearity.

Also, add a basic statistics package and unit tests for same.
Indentation fix.
Remove the summations of the cross products call.
This isn't required in the correlation computation.
Population standard deviation function and unit test.