TrackMate_: WIP redesign: fix some interactive tests

Signed-off-by: Jean-Yves Tinevez <jean-yves.tinevez@pasteur.fr>
TrackMate_: WIP redesign: fix some minor bugs in actions

Signed-off-by: Jean-Yves Tinevez <jean-yves.tinevez@pasteur.fr>
TrackMate_: WIP redesign: fix listening to display settings changes

Signed-off-by: Jean-Yves Tinevez <jean-yves.tinevez@pasteur.fr>
TrackMate_: WIP: work on making detection previewable

when configuring the chosen spot detector in the GUI, we have a preview
button that should be able to execute the detection process and display
its results on the - whatever view we have. See Johannes for this last
point.
Signed-off-by: Jean-Yves Tinevez <jean-yves.tinevez@pasteur.fr>