Enable more complex (user-provided) partition allocation

[gregorgorjanc]

Sometimes we don't know partition allocation fully, so we could use fuzzy/probabilistic allocation where the P matrix elements would not be just 0 or 1, but could be any value from 0 to 1, with the constraint that sum of them must be 1.

This feature request opens a question on how a user would provide such information!? Factor levels formated in a specific way? Say, M|F would indicate that we should allocate 0.5 to M and 0.5 to F partition. Or something like that ...

@janaobsteter also points that this would be needed when we partition by sex and allocate to male founders 100% M partition, and to females founders 100% F partition (we need to think if this is indeed wrong and that 50:50 allocation would be more appropriate - given that this is how we manage Mendelian sampling terms throughout AlphaPart, but indeed for founders the Mendelian sampling term is their breeding value).