k Get BM with nt and dt.  Modifies array.
k Get BB with nt, dt, X0, and XT.  Modifies array.
k Get BB with BM, X0, and XT.  Returns array.  Or in-place?
* stats_m tests for mean, var, covar -- a la test_brdb_slice?
* other 565C SDE stuff ...
* plotter ...