Adding Hybrid System features

[johnaoga]

https://dionysos-dev.github.io/Dionysos.jl/previews/PR395/

[blegat]

My main concern is how you link the reset map and the guard of a transition in case you have several transitions with the same source mode and same target mode

@constraint(model, guard(mode == 0, mode == 1) => {T <= T_r + δ})
@constraint(model, reset_map(mode == 0, mode == 1) => {Δx == ...})

Maybe we could do something like

t = Transition(model, mode, 0, 1)
@constraint(t, T <= T_r + δ)
@constraint(t, Δx == ...)

This would allow to use JuMP macros to define the guard and reset maps and we just have to define JuMP.add_constraint(::Transition, ...)
If we want to be fancy, we can then add some syntactic sugar to do

add_transition!(model, mode, 0, 1) do t
    @constraint(t, T <= T_r + δ)
    @constraint(t, Δx == ...)
end

where t would also be of type Transition but it looks a bit nicer.
The Transition constructor will also get an argument to specify what type of switching it is.

[johnaoga]

I like this transition thing pretty much, let's go with that.