Merge branch release-2016 into release-2018

Change-Id: If84bee0ff744533c841532efbf29e6338c412c5a

diff --cc docs/manual/algorithms.tex
Simple merge

diff --cc docs/user-guide/mdp-options.rst
Simple merge

diff --cc src/gromacs/fileio/enxio.cpp
Simple merge

diff --cc src/gromacs/gmxana/gmx_genion.cpp
Simple merge