Closes #101

QRules adapter function

This PR makes it a lot easier to build AmpForm-DPD decay structures with QRules. All examples in the notebooks are now generated with QRules + AmpForm-DPD. Comes down to:

from ampform_dpd.adapter.qrules import to_three_body_decay

reaction = qrules.generate_transitions(...)
decay = to_three_body_decay(reaction)
builder = DalitzPlotDecompositionBuilder(decay, min_ls=True)
model = builder.formulate(reference_subsystem=1)

$\Lambda_c \to p K \pi$

In the lc2pkpi notebook, the resonances are now the same as the published study under https://lc2pkpi-polarimetry.docs.cern.ch.

Comparison plots match now 🎉

The reason was incorrect parity conservation on the production node in $J/\psi$ decays.