TrackMate_: put back the old DogDetector implementation.

The speed toll is too high.
Signed-off-by: Jean-Yves Tinevez <jean-yves.tinevez@pasteur.fr>
TrackMate_: Directly compute and use a LoG kernel.

Signed-off-by: Jean-Yves Tinevez <jean-yves.tinevez@pasteur.fr>
TrackMate_: playing and finding problems with the new imglib2 tools

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