TrackMate_: implement and use the new DoG detector.

Signed-off-by: Jean-Yves Tinevez <jean-yves.tinevez@pasteur.fr>
TrackMate_: code style change.

We now use the imglib2 code style in TrackMate.
Signed-off-by: Jean-Yves Tinevez <jean-yves.tinevez@pasteur.fr>
TrackMate_: DoG: use the threshold early.

Signed-off-by: Jean-Yves Tinevez <jean-yves.tinevez@pasteur.fr>