Input normalization in discretize

[schillic]

The set U below must be n-dimensional (it is multiplied by A later).

ReachabilityAnalysis.jl/src/Discretization/Forward.jl

Lines 124 to 125 in a7d0557

	U = next_set(inputset(ivp), 1)
	Eψ0 = sih(P2A_abs * sih(A * U, alg.sih), alg.sih)

This relies on the user having eliminated the input matrix B already. I think discretize should do that for you instead.

Suggestion: The methods for discretize do not dispatch on the algorithm but only normalize the system. Then they call an internal function _discretize, which then dispatches on the algorithm.