Bug when trying to open some temporal sequences

Issue : https://med.inria.fr/redmine/issues/1751
The problem comes from a test that checks if the number of frames per slice is the same for every slice. We define frames like images that are at the exact same sliceLocation. Or with these images, some sliceLocations may differ from 0.000..1 mm. So our algorithm considers this as a new slice (and not a frame).
In the end, for every slice we don't have the same number of frames.

To correct this bug, I've forced the sliceLocation to be a multiple of the spacing between the slices.

Reviewers : Flo and Olivier
Merger: Olivier