Add Adjust Spacing option

This option (off by default) allow the CLI to automatically adjust the
output spacing so the output image isn't misaligned with the input image.
Also correct open VotingResample.
Simplify workflow's resample spacing

Instead of a coordinates widget box, we can use instead a simple spinbox
that show the scale with which the image spacing can be resampled. This
echoes to what is done for the compute weight step.
Also, since the spacing adjustement is done is the CLI now, we can simply
delete what was done here.
Finaly, fix the go to voting resample.
Expose voting resample precedence in the workflow

This options are for advanced user.