Anomaly call likelihood

pass correct values to `anomaly_likelihood`, enable `Anomaly.MODE_LIKELIHOOD` 
and provide test (serving as an example how to use the Anomaly class)

Fixes #967 
Unused now. Yet there is (at least 1 ;) ) impl of sliding window, which I'd like to replace with this code. So I'd either: 
* what you say + a new class for sliding window (which MovingAvg will utilize)
* keep as is and the to-be-replaced sliding window will just use the slidingWindow returned here