Extend mul! to include alfa and beta

Author: lkdvos

src/tensors/diagonal.jl

@@ -207,9 +207,10 @@ end
 
 function LinearAlgebra.mul!(dC::DiagonalTensorMap,
                             dA::DiagonalTensorMap,
-                            dB::DiagonalTensorMap)
+                            dB::DiagonalTensorMap,
+                            α::Number, β::Number)
     dC.domain == dA.domain == dB.domain || throw(SpaceMismatch())
-    dC.data .= dA.data .* dB.data
+    mul!(Diagonal(dC.data), Diagonal(dA.data), Diagonal(dB.data), α, β)
     return dC
 end