SDE integration updated

Updates from SDETools toolbox migrated over. Several new private function, and much cleaner code. Output functions now supported. Better support for custom random functions. New NonNegativeFUN option. Better support for time varying epsilon and mu. Versions of sdeget() and sdeset() in main directory for general use.

Signed-off-by: Andrew D. Horchler <adh9@case.edu>