avoid not only division by zero, but also computing variance for short runs with insufficient resolution

Merge branch 'bugfix_dividebyzero' of https://github.com/timattox/lammps_USER-DPD into collected-small-bugfixes

e.g. If neighbor list(s) are never rebuilt, the Neigh time will be zero.

This closes #336

This reverts commit 51e52b47.

get PairTableKokkos to inherit from PairTable (also fix GPU)

synchronize pppm/cg with changes in pppm and remove block on triclinic

Fixed bug in lamda_box_corners function

Initializing pointers in neighbor.cpp

Fix nvk implemented

GitHub tutorial update

Fix momentum kokkos

Kokkos bugfixes

Update Colvars library to version 2016-12-22

USER-DPD updates

Merge branch 'github-tutorial-update' of https://github.com/Pakketeretet2/lammps into github-tutorial-update

some formatting updates and text rewrites for your pull request

forgot to extract this change when
separating the commits for PairTableRX
and PairTableKokkos.