fix recenter

Hi all,
This is not really a question, I just think that the recenter command should be changed so that it can move systems a large distance on the first timestep. I think it is a lot to ask for someone to have to engineer their lmp file to have whatever they want to center be at that position already. I just had a simulation crash, and that seems to be the problem. It would be best if the algorithm could deal with that special case. I understand this might be difficult, but I don’t think it would be impossible.

Before you do a run, you can compute the COM of a system,
via the variable syntax for xcm(). Then you could
use the displace_atoms command to shift the system to
wherever you wish. Would that do what you want?