Uncertainty TODO

[baggepinnen]

• Go through docs and make sure all places where there is an extra 1.0I, ss() etc. are made smoother.
• ss can not be built from deltas

a = 10*(1 + δr())
P = ss([0 a; -a 0], I(2), [1 a; -a 1], 0) # fail

• For siso, Incorporate circle fitting in examples with parametric uncertainty. Fit circle to obtain single complex perturbation. Fit rational function to radii.
• initialize upper bound of ssv with opnorm and lower bound with spectral radius.
• Better support for real uncertainy