Have the run detection be longer than a threshold

Signed-off-by: Jean-Yves Tinevez <jean-yves.tinevez@pasteur.fr>
JUnit test for the velocity thresholder.

One minor use case is not covered, but listed in the test.
Signed-off-by: Jean-Yves Tinevez <jean-yves.tinevez@pasteur.fr>
Work debug method.

Signed-off-by: Jean-Yves Tinevez <jean-yves.tinevez@pasteur.fr>
Velocity macro analysis: estimates velocity threshold automatically.

Use the median of all track linear valocities.
Signed-off-by: Jean-Yves Tinevez <jean-yves.tinevez@pasteur.fr>