[ODE] StepFast1 documentation

[David Whittaker]

Hey everybody,

I posted some documentation on the StepFast1 algorithm on my website at
http://www.csworkbench.com/stepfast-doc.html .  All constructive criticism
is welcomed.  Let me know if you want more or less explanation, graphics,
or anything.  Hmmm, I should probably say a little more about the
stepsize/iterations/autodisablethreshold relationship.

Russ, I came up with just post-fixing SF1 on the stepfast-1 specific
functions.... it's a few characters shorter anyway.  Let me know if that
will/won't work.

David