Order struct in JunctionTree Module

[jpfairbanks]

@samuelsonric, what is going on with the Order struct?

# A total ordering of the numbers {1, ..., n}.
struct Order <: AbstractVector{Int}
    order::Vector{Int}
    index::Vector{Int}
end

It seems like this is just storing a permutation? Should this just be using things like sortperm and invperm from the standard library?