Datapoints are shifted in respect to system-cell

[yyyxam]

Whole dataset is starting on 0/0/0 and not in center of the first voxel.
This results in the whole set of datapoints being shifted half a voxel in each axis direction.
--> Easiest fix would be to shift the cell half a voxel back in all axis-directions
---> This is a problem in both atoms preview and main plot

[yyyxam]

Current fix is to roughly translate all points by half a voxel in each direction. This is hardcoded to work for testing data though