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 
no go? I find it nicer to indicate a sort of "hierarchy", `var` is method/class variable with some importance. `_var` is just a substitution with span of a few lines for better readability...?