Add some Maths functions for array: mean, variance, standard deviation...

[MaximeR]

When building test system, when I have analog measurement, I'm always using multiple measurement values for my test. Test is often based on mean and standard deviation.

I suggest to have some function in TestStand to calculate some standard statistics calculation like mean, standard devation, variance... on array (at least 1D array)

I don't count how many times I wrote this function or implement it in TestStand.