Implement alternative to clearsky model (Bayesian model)

[euronion]

Suggested by @FabianHofmann during our recent work on the FOSS paper.

Implement an alternative to the currently used clearsky model based on Bayesian statistics.

Detailed Description

n/a

Context

Relevance/Importance = ?

Possible Implementation

Reference:
Philippe Lauret, John Boland, Barbara Ridley,
Bayesian statistical analysis applied to solar radiation modelling,
2013,
https://doi.org/10.1016/j.renene.2012.01.049.