scprod has changed behavior in cmake branch

[wavepacket]

While translating Wavepacket to the cmake branch of the tensor library, I noticed a behavior change.

Previously, tensor::scprod(a, b) would calculate b^* \cdot a ("mathematician's" scalar product convention. Now, it is the other way around ("physicist's" convention), where the complex conjugate is taken from a.

As a physicist with backwards-compatibility concerns, I have no strong opinion either way. But it should be either reverted or marked as a breaking change.