Promote spaces for BraidingTensor (#258)

* Generalize BraidingTensor promotion

* Simplify implementation

* Fix

* Fix fix

Author: lkdvos

src/tensors/braidingtensor.jl

@@ -31,12 +31,15 @@ end
 function BraidingTensor{T}(V1::S, V2::S, adjoint::Bool=false) where {T,S<:IndexSpace}
     return BraidingTensor{T,S}(V1, V2, adjoint)
 end
+function BraidingTensor{T}(V1::IndexSpace, V2::IndexSpace, adjoint::Bool=false) where {T}
+    return BraidingTensor{T}(promote(V1, V2)..., adjoint)
+end
+function BraidingTensor(V1::IndexSpace, V2::IndexSpace, adjoint::Bool=false)
+    return BraidingTensor(promote(V1, V2)..., adjoint)
+end
 function BraidingTensor(V1::S, V2::S, adjoint::Bool=false) where {S<:IndexSpace}
-    if BraidingStyle(sectortype(S)) isa SymmetricBraiding
-        return BraidingTensor{Float64,S}(V1, V2, adjoint)
-    else
-        return BraidingTensor{ComplexF64,S}(V1, V2, adjoint)
-    end
+    T = BraidingStyle(sectortype(S)) isa SymmetricBraiding ? Float64 : ComplexF64
+    return BraidingTensor{T,S}(V1, V2, adjoint)
 end
 function BraidingTensor(V::HomSpace, adjoint::Bool=false)
     domain(V) == reverse(codomain(V)) ||