Feature/cloud cover probabilistic (#52)

* (PROB) Add two new probabilistic layers, modify a bit the descriptions

* Fix mistake

* (prob) Change naming for the beta layers

* Modify betas, add concave beta
Modify mixture (use trunc normals)

* Remove dummy class

* Fix naming

* Remove unused layer

* Fix mixture distribution for event shapes > 1

* Small change

* Fix shape handling for symbolic tensors

* Add censored normal layer

* Return an int instead of tensor for batch dims

* Remove experiental feature as it's not always reliable

* Change CensoredNormal layer to use a real censored rather than a truncated

* Add better description to 4paramBeta layer

Co-authored-by: Daniele Nerini <[email protected]>

* Correct doc

* Add a censored normal layer computed via softclipping

* Change to sample as mean is not implemented

* Make layer serializable

* Minor

* Add LogitNormal layer

* Do not use any mean() method to test the prob layers

* Test distribution params instead of its mean

* Consider special case with multivariate layers

* Rename to doublyCensored

* Remove softclipCensored

* Change layer to a mixture of Normals

* Refactor code

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Co-authored-by: louisPoulain <[email protected]>
Co-authored-by: Daniele Nerini <[email protected]>