makeLeafCoefficients: Make leaf coefficients
In treeDA: Tree-Based Discriminant Analysis

For a set of coefficients defined on a matrix of (potentially centered and scaled) leaf and node predictors, find the equivalent set of coefficients on just the leaves.

1	makeLeafCoefficients(sda.out, descendantMatrix, means, sds)

`sda.out`	A fitted sda object
`descendantMatrix`	A matrix describing the tree which was used, element (i,j) indicates whether leaf i is a descendant of node j.
`means`	If the original predictor matrix was centered, the means of the original predictor matrix, otherwise NULL.
`sds`	If the original predictor matrix was scaled, the sds of the original predictor matrix, otherwise NULL.