Add SententialDecisionDiagrams.jl as an optional dependency

[guyvdbroeck]

Add https://github.com/pedrozudo/SententialDecisionDiagrams.jl as an optional dependency (JuliaLang/Pkg.jl#1285).
At minimum, make it easy to convert the native SDD data structure to Julia structs in the LogicCircuit hierarchy, so we can do things like compute flows efficiently.

[khosravipasha]

I guess Requires.jl also should work perfectly for this. And the main useful integrations are:

1. Import Vtree from SDD.jl to Juice
2. Import SDDs from SDD.jl to Juice

Do we need anything else? Maybe later on case also add more interactive scenarios.