refactor: remove optional `prior` parameter from LLR.toPosteriorProbability

use `equal_priors` attribute instead
feat: IdentificationErrorRate components can be weighted

use ‘confusion’, ‘false_alarm’ and ‘miss’ parameters.
default behavior does not change.
style: PEP8
doc: ClassificationGMMUBM
refactor: ClusteringCalibration

better use of ‘equal_priors’ attribute
refactor: AuthenticationCalibration

follows style introduced in ClusteringCalibration
refactor: PIG{IntraModal|Identification}Edges

* PIGIntraModalEdges inherits from ClusteringCalibration
* PIGIdentificationEdges inherits from AuthenticationCalibration
* both inherit from PIGEdgeIOMixin (load/save)