mctools/ncrystal: NCrystal release 3.1.0

This release focuses on those inelastic scattering events that almost bring the neutron to rest, and which are in particular important for UCN (or VCN) production in neutron moderators. The main new features are a general improvement in inelastic scattering kernel sampling for UCN or near-UCN production events, as well as a new special UCN mode which can be used for biasing or variance reduction scheme in studies involving UCN production (e.g. moderators).

Please refer to the release 3.1.0 announcement page on our wiki for a slightly more detailed overview about this new release!