Gromacs dummy atoms

[skfegan]

The mass assigned to dummy atoms needs fixing. The Lennard-Jones terms need to be checked.

[skfegan]

Hannes modified FESetup/amber16/dat/antechamber/PARMCHK.DAT to add type du. When generating the morphs, parmchk2 is used to create a frcmod file that is then loaded into tleap to create the topology. This sets 1.00 as the mass of the dummy atom.

[tbwxmu]

I also get this bug. It seems changing PARMCHK.DAT is not enough within Ambertools2021.