Define (::ITensor / ::ITensor)

[mtfishman]

Define (::ITensor / ::ITensor) for the case when the second ITensor is a scalar:

julia> ITensor(2) / ITensor(3)
ERROR: MethodError: no method matching /(::ITensor, ::ITensor)
Closest candidates are:
  /(::KrylovKit.RecursiveVec, ::Any) at /home/mfishman/.julia/packages/KrylovKit/YPiz7/src/recursivevec.jl:33
  /(::KrylovKit.InnerProductVec, ::Any) at /home/mfishman/.julia/packages/KrylovKit/YPiz7/src/innerproductvec.jl:13
  /(::ITensor, ::Number) at /home/mfishman/.julia/dev/ITensors/src/itensor.jl:1578
Stacktrace:
 [1] top-level scope
   @ REPL[160]:1

julia> i = Index(2)
(dim=2|id=135)

julia> randomITensor(i) / 2
ITensor ord=1 (dim=2|id=135)
ITensors.NDTensors.Dense{Float64, Vector{Float64}}

julia> randomITensor(i) / ITensor(2)
ERROR: MethodError: no method matching /(::ITensor, ::ITensor)
Closest candidates are:
  /(::KrylovKit.RecursiveVec, ::Any) at /home/mfishman/.julia/packages/KrylovKit/YPiz7/src/recursivevec.jl:33
  /(::KrylovKit.InnerProductVec, ::Any) at /home/mfishman/.julia/packages/KrylovKit/YPiz7/src/innerproductvec.jl:13
  /(::ITensor, ::Number) at /home/mfishman/.julia/dev/ITensors/src/itensor.jl:1578
Stacktrace:
 [1] top-level scope
   @ REPL[164]:1