mis-configured Control Law example

The Control Law example with prediction was mis-configured.
The multiplication of two systems (A*B) is not the same
as series(A,B) in the Octave control toolbox.  Oddly, it
does seem to be the same as (B*A).  In any case, series()
should be used since it is more explicit.
Added feedback with two inputs example

An example has been added for creating a feedback system
with two inputs using the Octave control toolbox.
The inputs are *indicies* instead of names like all the
other functions.  Once that issue was resolved it was
fairly straightforward.