fix error message for wrong set in inds()

[starsfordummies]

if you call inds(::Chain) with the wrong set = option, Tenet throws an obscure error - I don't know if this is due to a wrong use of MethodError, I changed it for an ArgumentError and it works. I also added some extra info, so now it throws

julia> inds(psi, set=:sergio)
ERROR: ArgumentError: unknown query: set=sergio.
        Possible options are:
        :all, :open :inner :hyper :parallelto
        For Quantum also :physical :virtual

[mofeing]

Thanks @starsfordummies! Just a small suggestion