More documentation

See merge request !348

Merge branch '429-negative-distances-at-medium-transitions-with-activated-magnetic-field' into 'master'

Resolve "Negative distances at medium transitions with activated magnetic field"

Closes #429

See merge request !379

Resolve "Rare FPE in Cascade.inl debug printout"

Closes #439

See merge request !380

added pdg codes for nuclei

See merge request !378

Resolve "libstdc++11 not available on MacOS"

Closes #428

See merge request !377

Resolve "Trajectories crossing observation plane"

Closes #427

See merge request !369