Plus42 algebraic expressions update

[Vincent Weber]

Thanks Thomas, understood.
I had missed DDAYS for some reasons.
As for financial functions, they are part of the 27S (for some of them like USPV) and the 19B (more complete set with direct FV, PMT...), but anyway the good part is that since you will allow user-defined functions, we will always been able to add whatever is missing with such a UDF

Cheers