Automatically compute sign of decay helicity coupling

[redeboer]

[mmikhasenko]

In serialization, we distinguish, a recoupling factor (fundamental, mathematical) and a coupling (physical unit). The couplings in the cascade decays cannot be measures all, but their product, defined as the weight.
The coupling is one of three types ("ls", "parity", and 'norecoupling"). it is either 0, or 1, or a Clebcsh.

The weight in contrast is an arbitrary complex value.

[mmikhasenko]

adding the explanation of the recouplings here
https://github.com/RUB-EP1/amplitude-serialization/blob/main/description.md#vertices