update to doc pages for new coreshell pair styles

fix segfault bug in fix rigid/small found by regression testing

add coul/wolf/cs and born/coul/wolf/cs pair styles for CORESHELL package

Allow rigid body generation from custom properties

Compute energy correctly for bond style gromos

Fix a Colvars error that was hidden by the previous segfault

add/correct code to define rigid bodies with atomstyle/atomfile variables and via custom per-atom properties

Import segfault fix in Colvars module

cross ref fix deform and new fix nvt/uef in doc pages

small updates to recently added docs and rename of an example dir

USER-UEF package for extensional flow

fix rhok - biasing long-range order

Add gromos bond style

Avoid checking region when not specified

USER-DPD small updates

Bug fix for unexpected case where a Intel bonded style is specified but there are no types

refactoring of neighbor history

USER-INTEL: Bug fix for case where a bond/angle/dihedral/improper style is specified, but there are no bond/... types and therefore no allocation.

Propogate the efaa4c67 changes to npair_ssa_kokkos from npair_kokkos that
support the new neigh_modify exclude molecule/intra and /inter options.
Note: npair_ssa_kokkos could inherit from npair_kokkos to avoid this kind
of missed change. Unfortunately, inheritance from templated classes is
both tricky and messy, and not worth the complexity in this case, IMHO.